ADAMTS13 Mutations Research Articles

Value of Prophylactic Plasma Treatment and Incidence of Acute Episodes in Patients Enrolled in the International Hereditary Thrombotic Thrombocytopenic Purpura Registry

Background: Hereditary thrombotic thrombocytopenic purpura (hTTP), or Upshaw-Schulman syndrome, is a rare thrombotic microangiopathy due to a severe congenital deficiency of ADAMTS13 resulting from bi-allelic ADAMTS13 mutations. As in other plasma factor deficiencies, treatment consists of replacement of the missing ADAMTS13, which can currently be attempted with fresh frozen plasma, solvent/detergent plasma or plasma-derived factor VIII/Von Willebrand factor concentrates. Although prophylactic plasma infusions prevent acute episodes in many but not all hTTP patients, current treatment guidelines state conditional recommendations for prophylaxis outside of pregnancy, because evidence supporting the burdensome plasma prophylaxis in hTTP patients is scarce. Aims: Prospective evaluation of the incidence of acute episodes occurring in hTTP patients during periods with and without prophylactic plasma treatment. Methods: All patients with a confirmed diagnosis of hTTP enrolled in the International hTTP Registry between January 01, 2006 and December 31, 2021 were eligible for study. Diagnosis of hTTP was based on persisting ADAMTS13 activity <10%, bi-allelic ADAMTS13 mutations, and/or an infusion trial with full recovery and a half-life of plasma ADAMTS13 of around 60 hours. We recorded the patients' detailed medical history at enrollment and then collected prospective data on the clinical course, treatment modalities and laboratory values through site-visits and case report forms completed by treating physicians during annual visits or at occurrence of acute TTP episodes. Patients were followed until December 31, 2022 (database lock), death, or loss to follow-up, whatever came first. This post-hoc analysis evaluated acute TTP episodes during follow-up, stratified by periods on prophylaxis and without prophylaxis. Patients could contribute follow-up time to both periods (strata), but never simultaneously and gestation periods were excluded. Minimum criterion for long-term prophylaxis was defined as at least one monthly plasma infusion over a period of ≥ 6 months. Results were reported using descriptive statistics without formal statistical comparison and incident rates of acute TTP events were calculated per 1000 person-years with corresponding 95% confidence intervals (CIs). Results: At the end of December 2021, the International hTTP Registry had 182 confirmed hTTP patients eligible for this analysis that were followed for a median period of 3.6 (range, 0-18.5) years. The gender distribution showed more female (n=98, 53.8%) than male (n= 84, 46.2%) patients enrolled, a disparity likely related to a surge of diagnosis in women due to pregnancy complications. During prospective follow-up, 47 (25.8%) hTTP patients never had prophylactic treatment, while 135 (74.2%) received any form of prophylactic treatment, including long-term prophylaxis in 117 (86.7%). Patients who received any prophylactic treatment during follow-up had an incidence rate (95% CI) of acute TTP episodes of 272.4 (230.8-319.3) per 1000 person-years while receiving prophylaxis and of 520.4 (401.6-663.3) per 1000 person-years during periods without prophylaxis (Table 1). In the patients on long-term prophylaxis, the incidence rate of acute TTP episodes was 267.1 (226.0-313.6) per 1000 person-years in periods with prophylaxis, and 879.6 (664.4-1142.2) per 1000 person-years without prophylaxis. Irrespective of treatment interval, about half of patients on prophylaxis had break-through events, with the highest incidence rate observed in the group of patients receiving plasma products weekly, possibly reflecting their more precarious or severe disease course. Conclusions: In this large hTTP patient cohort observed for five years on average, we confirm the incidence rate of acute events as reported by Tarasco et al. (Blood 2021;137;3563-75). Here, we demonstrate for the first time that hTTP patients with disease courses requiring prophylaxis benefit from this burdensome treatment, which was most evident in patients on long-term prophylaxis. Current treatment options are however insufficient to suppress residual disease activity leading to break-through events observed in half of the patients on prophylaxis. Novel therapies, such as recombinant ADAMTS13, with the potential of reaching higher plasma levels, will likely overcome limitations of current treatment options.

Insight into the Natural History of Hereditary Thrombotic Thrombocytopenic Purpura: Short- and Long-Term Outcomes in a Longitudinally Followed Large Patient Cohort of the International Hereditary TTP Registry

Background: Hereditary thrombotic thrombocytopenic purpura (hTTP), also known as Upshaw-Schulman syndrome, is an ultra-rare, thrombotic microangiopathy resulting from bi-allelic ADAMTS13 mutations and severe congenital ADAMTS13 deficiency. Clinical presentation includes thrombocytopenia, hemolytic anemia and symptoms of organ ischemia (primarily of brain, heart, gastrointestinal tract and kidneys) during acute episodes and pregnancy complications, but less explicit symptoms (abdominal discomfort, headaches, neurocognitive problems or fatigue) responding to plasma therapy are also common. Standard of care consists of replenishing ADAMTS13 using plasma/plasma-derived blood products to treat acute episodes as well as prophylactically to prevent morbidity and mortality. Improvement of hTTP disease management requires better understanding of the treatment burden and possible shortcomings as well as short- and long-term clinical outcomes. Aims: Description of the natural history of hTTP in a prospectively followed large patient cohort with a focus on demographic and clinical characteristics, as well as on the occurrence of acute TTP episodes, comorbidities and mortality. Methods: Eligible for the current study were patients with a confirmed hTTP diagnosis (lasting ADAMTS13 activity <10%, bi-allelic ADAMTS13 mutations, and exclusion of acquired, autoimmune TTP) enrolled before December 31, 2021. In an ambidirectional approach, the registry assesses the patients' detailed medical history at enrollment (retrospective data) and then prospective clinical, molecular and observational data through questionnaires completed by treating physicians during annual visits or at occurrence of acute TTP episodes. Patients were followed by the International hTTP Registry until December 31, 2022 (end of current analysis), death, or loss to follow-up, whichever occurred first and results were reported using descriptive statistics. Results: At the end of December 2021, the International hTTP Registry had enrolled 182 confirmed hTTP patients from 49 sites in 20 countries, who were followed for a median of 3.6 (range, 0-18.5) years. The cohort included more female (n=98, 53.8%) than male (n= 84, 46.2%) patients, a gender disparity observed in adult patients because of increased diagnosis in women related to pregnancy complications. The patients were mostly White/Caucasian (n=111, 61.0%), followed by Asian (n=50, 27.5%), Black (n=2, 1.1%) and other ethnicities (n=19, 10.4%). Although 46.2% of the patients reported first symptoms of hTTP in the perinatal period (0-3 months), the median ages (ranges) at diagnosis and registry enrollment were 19.1 (0-69.9), and 30.4 (0.1-75) years, respectively. Prior to enrollment, 85.7% of patients had experienced at least one acute TTP episode with a mean (SD) of 4.3 (4.5) reported events per patient. The medical history was notable for transient ischemic attacks or strokes in 31% of hTTP patients, followed by arterial hypertension in 20%, chronic kidney disease in 12%, migraines/severe headaches in 8.2%, and seizures in 7.7%, respectively. During prospective follow-up 82 of 182 patients (45.1%) experienced 265 acute TTP episodes resulting in an overall event rate of 296.7 (95% confidence interval [CI]: 262.0-334.6) per 1000 person-years. Eight hTTP patients died during follow-up, five of them were on regular plasma prophylaxis. The causes of death were acute TTP episodes associated with cerebral (n=3; patient ages 33, 44 and 52 years) or cardiac (n=3; 39, 49, and 56 years) events, and unknown in two patients (75 and 79 years). Conclusions: The clinical burden due to recurrent acute TTP episodes and resulting neurological, cardiovascular and renal sequelae and other comorbidities is significant. Delayed diagnosis and insufficient treatment likely contributed to the observed morbidity and early mortality. Awareness, timely diagnosis and sufficient ADAMTS13 replacement therapy (for acute episodes and prophylactically) are crucial for improving short- and long-term clinical outcomes and disease burden in hTTP.

Estimating the Population-Based Prevalence of Congenital Thrombotic Thrombocytopenic Purpura Using Large-Scale Sequencing Data

Introduction Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder caused by severe ADAMTS13 deficiency. This severe deficiency (<10%) is classified into two forms of acquired or hereditary TTP. Acquired TTP is either due to circulating autoantibodies inhibiting ADAMTS13 activity or increasing its clearance, whereas congenital TTP results from homozygous or compound heterozygous ADAMTS13 mutations (cTTP, Upshaw-Schulman syndrome). Because of ADAMTS13 defects, an abnormal amount of ultra-large von Willebrand factor multimers is concentrated, resulting in the formation of platelet-rich microthrombi in the circulation. Given that the true prevalence of cTTP is not established, we sought to leverage the availability of exome or genome sequences of very large numbers of individuals (genome Aggregation Database, gnomAD) to estimate the worldwide and within-population prevalence of cTTP. We also aimed to examine the global mutational landscape of ADAMTS13. Methods Exome and genome sequencing data of 141,456 subjects of gnomAD were extracted and analyzed for ADAMTS13. We comprehensively reviewed literature to identify all ADAMTS13 variants that have been associated with cTTP so far. In addition, all variants reported to be associated with cTTP in HGMD and/or LOVD datasets were included. Finally, we searched for ADAMTS13 variants in ClinVar that have been classified as “pathogenic” or “likely pathogenic”. The following gnomAD variants were considered pathogenic: variants associated with cTTP in HGMD/LOVD; nonsense, frameshift, inframe deletion/insertion variants; splicing variants affecting the first/last two intronic nucleotides; splicing variants affecting the first/last eight intronic nucleotides predicted deleterious by 4 different in silico tools; missense variants predicted deleterious by 7 different in silico tools. Using the frequencies of known or predicted pathogenic variants in ADAMTS13 of the gnomAD population (n= 141,456), we estimated the prevalence of individuals homozygous or compound heterozygous for cTTP (assuming Hardy-Weinberg equilibrium). Results Following quality controls and removing variants with no clear association with cTTP, we found that 302 different ADAMTS13 variants have been so far reported to cause cTTP in the literature, HGMD and LOVD as well as ClinVar. We then collected high-quality data from gnomAD population including 141,456 subjects with different ethnicities: 12,487 Africans/African Americans, 17,720 Latinos/Admixed Americans, 5,185 Ashkenazi Jewish, 9,977 East Asians, 12,562 Finnish Europeans, 64,603 non-Finnish Europeans, 15,308 South Asians, and 3,614 persons without an assigned ethnicity. We identified a total number of 2212 variants within ADAMTS13 among 282,912 alleles analyzed in the gnomAD population. Of these, following a conservative approach, 250 different variants were pathogenic; 83 reported to be associated with cTTP and 167 predicted to be pathogenic. Among a maximum number of 282912 alleles analyzed, 2166 alleles were affected by novel or reported variants. Of which, 53% of the affected alleles were due to known pathogenic variants and the remaining 47% were due to novel predicted variants. Considering all pathogenic variants (n=250) and only those reported (n=83), we estimated an overall cTTP prevalence of 17 and 59 individuals per million people, respectively (Table 1). Considering reported variants only, the highest prevalence of cTTP was estimated in Europeans and Finnish population (30 and 26 per 10 6), followed by Latinos/Admixed Americans (14 per 10 6) and Africans/African Americans (6 per 10 6). East and South Asian ethnicities had a lower estimated prevalence of 4 and 3 per 10 6, respectively. Ashkenazi Jewish population had the lowest estimated prevalence of cTTP (0.6 per 10 6) among all populations (Table 1). Conclusion We have attempted to estimate the worldwide and within-population prevalence of cTTP using available genome/exome sequencing data of 141,456 individuals. Our results reveal that putative disease alleles and cTTP-associated variants are more prevalent than expected and the true cTTP prevalence is more than ten times higher than was reported. This finding suggests that a large number of patients might be undiagnosed. We also established the mutational burden of ADAMTS13 by identifying 167 novel variants in addition to the 302 previously reported.

Novel ADAMTS13 mutations in a patient with congenital thrombotic thrombocytopenic purpura

ABSTRACTCongenital thrombotic thrombocytopenic purpura (TTP) is a rare autosomal recessive genetic disorder caused by mutations in the ADAMTS13 gene. Approximately 200 mutations of the ADAMTS-13 gene have been identified, although only a few have been characterized through in vitro expression studies. We conducted an investigation on a male congenital TTP patient with reduced plasma levels of ADAMTS13 activity. DNA sequence analysis revealed two mutations on chromosome 9 (1.9q34.2) in the patient’s ADAMTS13 gene. One mutation was a non-synonymous mutation (exon 5: c.A530G: p.Y177C), while the other was a nonsense mutation (exon 21: c.G2651A: p.W884X). Both mutations were found to be heterozygous. The patient’s parents had no history of thrombocytopenia or neurological symptoms. DNA sequence analysis showed the patient’s father was a heterozygote for the nonsense mutation of the ADAMTS13 gene (exon 21: c.G2651A: p.W884X), while the mother was a heterozygote for the non-synonymous mutation of the ADAMTS13 gene (exon 5: c.A530G: p.Y177C). To investigate the mechanism behind ADAMTS13 deficiency in this patient, wild type (WT), ADAMTS13 p.Y177C, and ADAMTS13 p.W884X were transiently expressed in 293-6E cells. Expression studies revealed a significant reduction in enzyme activity and secretion, although the protease was detected within the cells. The 3D structures of the natural and mutated ADAMTS-13 proteins were partially reconstructed using the Phyre2 web server. The mutation that replaces the tyrosine residue at amino acid position 177 with cysteine may result in decreased steric hindrance and a looser structure. This mutation affects the binding of calcium ions and the secretion of the enzyme from intracellular to extracellular compartments.

Adamts13 Mutation Revealed By a Recurrent Ischemic Stroke in a Young Male Patient Responding to Steroid Therapy Alone: A Case Report

ADAMTS 13 deficiency can lead to recurrent cryptogenic strokes, especially among young patients. We describe the first case of recurrent stroke due to ADAMTS13 deficiency that responded to steroid therapy alone.

Characteristics and genotype–phenotype correlations in ADAMTS17 mutation–related Weill–Marchesani syndrome

Weill–Marchesani syndrome (WMS) manifests as ectopia lentis (EL), microspherophakia and short stature, which is caused by ADAMTS10, LTBP2, or ADAMTS17 gene defects. This study aims to investigate the characteristics and genotype–phenotype correlations of WMS with ADAMTS17 mutations. WMS patients with ADAMTS17 variants were identified by whole-exome sequencing from 185 patients with EL. All the included patients underwent comprehensive ocular and systemic examinations. ADAMTS17 variants were reviewed from included patients, published literature, and public databases. Bioinformatics analysis, co-segregation analysis, species sequence analysis, and protein silico modeling were used to verify the pathogenic mutations. A total of six novel ADAMTS17 mutations (c.1297C > T, c.2948C > T, c.1322+2T > C, c.1716C > G, c.1630G > A, and c.1669C > T) were identified in four WMS probands in our EL cohort (4/185, 2.16%). All probands and their biological parents presented with apparent short stature compared with the standard value. In particular, one child was detected with valvular heart disease, which has not previously been reported in patients with ADAMTS17 mutations. Conserved residues were greatly affected by the substitution of amino acids caused by these six mutations. Short stature could be considered a clue for EL patients with ADAMTS17 mutations, and much more attention needs to be paid to heart disorders among these patients. This study not only reported the characteristics of ADAMTS17 mutation-related WMS but also helped to recognize the genotype–phenotype correlations in these patients.

A Novel Missense Mutation in the TGF-β-binding Protein-Like Domain 3 of FBN1 Causes Weill-Marchesani Syndrome with Intellectual Disability.

Weill-Marchesani syndrome (WMS) is a rare connective tissue disorder characterized by locus heterogeneity and variable expressivity. Patients suffering from WMS are described by short stature, brachydactyly, joint stiffness, congenital heart defects, and eye abnormalities. This disorder is inherited in two different modes; the autosomal dominant form of the disease occurs due to a mutation in FBN1, and the recessive form results from mutations in ADAMTS10, ADAMTS17, or LTP2 genes. The family recruited in this study was a consanguineous Iranian family with an intellectually disabled girl referred to the Sadra Genetics laboratory, Shahrekord, Iran. The clinical history of family members was investigated. Whole-Exome Sequencing (WES) for the proband was performed. Sanger sequencing was used to assess the segregation of candidate variants in the other family members. Whole-exome sequencing analysis revealed a novel heterozygote mutation in the proband located at the third TGF-β-binding protein-like (TB) domain of the FBN1 gene (NM000138: c.2066A>G: (p. Glu689Gly), NP_000129.3, in exon 17 of the gene). Co-segregation analysis with Sanger sequencing confirmed this mutation in the affected members of the pedigree. Our findings represent an autosomal dominant form of specific WMS resulting from a substitution mutation in the FBN1 gene. In addition to the typical manifestations of the disorder, mild intellectual disability (ID) was identified in the 8-year-old proband. Given the fact that ID is primarily reported in ADAMTS10 mutated cases, this family was clinically and genetically a novel case.

Novel ADAMTS13 mutation in a family with three recurrent neonatal deaths: a case report and literature review

BackgroundUpshaw-Schulman syndrome (USS) is rare, autosomal recessive, hereditary thrombotic thrombocytopenic purpura (TTP) caused by variants in a disintegrin-like and metalloprotease with thrombospondin type 1 motif (ADAMTS13). USS has a heterogeneous clinical course, and most symptoms overlap with other diseases. Early diagnosis may have important implications for the patients. We found novel ADAMTS13 mutation and explored the clinical features and prognosis of newborn-onset USS to increase awareness of the disease.Case DescriptionThe same, non-consanguineous couple had three unexplained neonatal deaths. The symptoms of the three infants were mainly severe jaundice, anemia and thrombocytopenia after birth, which was consistent with the reported USS symptoms of neonates and died rapidly suddenly in the during rescue efforts. By using whole-exome sequencing (WES) for the study family, we found a novel heterozygous compound in ADAMTS13 (c.1187 (exon10) G>A (p.C396Y)/c.1595 (exon14) G>T (p.C532F)) that was carried by the three newborns originating from father and mother respectively. We reviewed nine published studies of newborn-onset USS and compared our cases for clinical symptoms and laboratory testing. All nine published cases were diagnosed by ADAMTS13 activity; in seven cases gene mutation analysis was performed and eight cases were still alive at the time of publication.ConclusionsThe case has added clinicians’ awareness of the diagnosis and treatment of USS. A novel rare mutation in ADAMTS13 broadens the spectrum of genetic causes of this rare disorder and expands the phenotypic spectrum.

Long-Term Renal Outcomes in Hereditary TTP Patients: Data from the International Hereditary TTP Registry

IntroductionHereditary thrombotic thrombocytopenic purpura (hTTP) is an ultra-rare thrombotic microangiopathy caused by autosomal recessively inherited severe ADAMTS13 deficiency. In respect to organ damage, we recently reported a heterogeneous clinical course with some patients having various degrees of organ damage while others are almost asymptomatic*. The long-term consequences of hTTP are still not fully known.MethodsWe analyzed the prevalence and development of renal disease in confirmed hTTP patients in the International Hereditary TTP Registry until July 2021. We studied the onset of kidney disease, the presence of additional co-morbidities and the possibility of a specific genotype-phenotype correlation. We classified different renal diseases of our hTTP patients, according to the ICD-10 code (version 2016) as described in Table 1.ResultsThirty-five (21%) of 163 confirmed hTTP patients of the International TTP Registry with a mean age at enrolment of 38.2 years had kidney disease. 80% were Caucasian, 8.5% Asian and 11.5% indicated other ethnicities.According to the ICD-10 code classification, two patients had acute kidney disease (AKI, ICD code N17) not specified during acute TTP episodes. Among 18 patients with general CKD, we could identified three patients with chronic kidney disease (CKD, ICD code N18) stages 1-2; four with CKD stage 3, and four patient with CKD stage 5. In two patients, kidney disease was unspecified (ICD code N19). Five patients had diagnoses of certain specific renal diseases, such as acute glomerulonephritis (ICD code N00), unspecified nephritis syndrome (ICD code N05), recurrent and persistent hematuria (ICD code N02), and calculus of the kidney (ICD code N20) (Table 1). Seven patients developed end-stage renal disease requiring renal replacement therapy (ICD code Z99.2), which was temporarily needed in four additional patients (Z49.2). Two patients underwent kidney transplantation (ICD code Z94) (Table 1).The 163 hTTP patients experienced 625 acute disease episodes, of which 108 (17%) were associated with acute renal failure. 21/163 (13%) acute episodes were treated with hemodialysis. After experiencing several hTTP episodes with acute renal failure, 15 patients developed CKD at different stages.26/35 (74%) hTTP patients with kidney disease presented also other co-morbidities: hypertension in 14 patients, 10 and 18 patients had suffered from transient ischemic attacks and/or strokes, and six patients had suffered from a myocardial infarction. We observed no apparent correlation between onset of CKD and presence of co-morbidities.Regular plasma prophylaxis was introduced in 26/35 hTTP patients with kidney disease; in the majority of them (64%) plasma treatment was started due to CKD or after CKD diagnosis.Of the 35 patients with renal disease, 15 were homozygous and 20 compound heterozygous ADAMTS13 mutation carriers. The most known ADAMTS13 mutation c.4143_4144dupA counts 33% of the whole hTTP patients in our database (54/163 patients). It was the most represented mutations in our cohort of hTTP patients with renal disease (60%, 21/35): 11 homozygous and 10 compound heterozygous carriers. Nevertheless, we did not observe a specific genotype-phenotype correlation.ConclusionsOur analysis of the International Hereditary TTP Registry cohort (at present 163 patients) showed that the majority of patients had a diagnosis of hTTP before a diagnosis of kidney disease, especially CKD. We could not identify a correlation with the onset of additional co-morbidities or with the genotype; nevertheless we cannot exclude that it may be present. Considering that 43% (15/35) patients developed CKD after several acute episodes with acute renal failure, a closer and attentive care for those patients not yet developing CKD to avoid or delay the onset is highly recommended. Hence, to evaluate the contribution of acute hTTP episodes and of other co-morbidities to the development of kidney disease requires further in depth analyses. More frequent and long-term follow-up visits are needed to better understand the long-term outcome and development of kidney disease in hTTP patients.* Tarasco et al, Blood 2021 [Display omitted] DisclosuresMatsumoto: Sanofi: Consultancy; Takeda: Consultancy; Alexion Pharma: Consultancy; Asahi Kasei Pharma: Research Funding; Chugai Pharmaceutical: Research Funding; Alfesa Pharma: Patents & Royalties: ELISA for measuring ADAMTS13 activity. Lämmle: Takeda: Membership on an entity's Board of Directors or advisory committees; Ablynx: Membership on an entity's Board of Directors or advisory committees, Other: Travel Support, Speakers Bureau; Baxter: Other: Travel Support, Speakers Bureau; Alexion: Other: Travel Support, Speakers Bureau; Siemens: Other: Travel Support, Speakers Bureau; Bayer: Other: Travel Support, Speakers Bureau; Roche: Other: Travel Support, Speakers Bureau; Sanofi: Other: Travel Support, Speakers Bureau. Kremer Hovinga Strebel: Baxalta US Inc: Other: grant; Shire: Consultancy, Speakers Bureau; Ablynx: Consultancy, Speakers Bureau; Federal Office of Public Health: Consultancy; Insel Gruppe AG: Current Employment.

Prevalence of Stroke and Cognitive Impairment in Patients with Hereditary Thrombotic Thrombocytopenic Purpura

Hereditary thrombotic thrombocytopenic purpura (HTTP) is a rare autosomal recessive disorder caused by biallelic mutations in the ADAMTS13 gene. From 3 large case series reported in 2019 (UK Registry, Blood 2019; 133(15):1644; International Registry, Haematologica 2019 104(10);2107-2115; Borogovac, et al. Blood Advances 2019; 3(23):2973-6), we know that the clinical presentation of HTTP can range from asymptomatic disease to significant morbidity and early mortality. Stroke is the most common and most severe morbidity reported in 25-31% of patients (pts) with HTTP. However, due to a short duration of follow-up (median age of last follow up of 24-26 years (yrs) old) in these 3 case series, the morbidities in older pts are unknown.We conducted a descriptive study with adult and pediatric pts within the US who have a diagnosis of HTTP by ADAMTS13 activity level of <10% and biallelic ADAMTS13 mutations and are enrolled in the International HTTP Registry. Previously reported studies have had limited long-term follow up. Our objective was to characterize the clinical features of the disease and its impact on patients over multiple decades. We determined the frequency and age of onset of stroke and other neurologic and neuropsychiatric symptoms. Each pt and/or their parents (if children) completed a 30-60 minute phone interview with the first author to learn about their daily lives, their medical history and their limitations or disabilities. The interviews used a semi-structured discussion guide tailored to their age group. Chi-square analysis or Fisher's exact test were performed to assess the difference in frequency of symptoms in pts with or without history of stroke. To assess the incidence rate of stroke depending on prophylaxis use, a rate ratio was performed using stokes as events and person-time yrs on or off prophylaxis as the denominator.A total of 26 pts (or their parents) were interviewed from April 2020 to July 2021. The median age was 37 with 24 adults (ages 19-63) and 2 children (ages 1, 12). Our sample was predominantly female (73%), white (88%), and with a college or higher education (75%). Stroke was reported in 16 pts (62%) with a median age for first stroke of 26 yrs (newborn-53 yrs). Residual symptoms were reported in 10 (63%) stroke pts. Six (23%) pts have been on stroke-related disability, beginning at a median age of 40 yrs (18-53 yrs). Twenty-four of 25 (96%) pts reported recurrent neuropsychiatric symptoms (the one infant was excluded, Table). The most common symptoms were recurrent headaches (22 pts), migraine with aura (14 pts), poor concentration (16 pts), and forgetfulness (11 pts). There was no difference in the frequency of these symptoms in pts with or without history of stroke except dysarthria was more common in pts with a history of stroke (Table). Twenty of 24 (83%) pts who have received plasma within their lives have had an allergic reaction, most commonly rash or itching in 70%, followed by shortness of breath or chest pain in 20%, and 2 pts (10%) had anaphylaxis. Two pts reported no allergic reaction to plasma. Sixteen pts (62%) are currently on prophylaxis. Prophylaxis was not shown to be protective of stroke with a calculated rate ratio of 0.76 (95% CI 0.26-2.18). A total of 4 pts had a stroke while on prophylaxis, of whom 2 had reported not missing any doses. The other 2 pts had missed a dose at the time of stroke or had been receiving prophylaxis at a prolonged interval of every 3 weeks, indicating inadequate administration.In conclusion, HTTP pts suffer from significant neurologic morbidity with an overall occurrence of stroke in 62%, more than twice the rate from prior reports. Our median age of follow-up (37 yrs) is older than in previous reports (24-26 yrs). Here, 56% of first strokes occurred at age 25 yrs or older. Importantly, the penetrance of stroke as a life event increases with age at follow-up and is 100% in pts over 50 yrs (Figure). Our observational study did not demonstrate that the use of prophylaxis significantly decreases the risk of stroke. Limitations include small sample size and non-randomized trial design. Neuropsychiatric symptoms occurred in 96% of pts independent of a history of stroke, possibly related to recurrent microvascular thrombosis. Future prophylaxis with recombinant ADAMTS13 (currently completing its phase 3 trial) will be make self-administration more convenient, and may be more effective than plasma. [Display omitted] DisclosuresKremer Hovinga Strebel: Baxalta US Inc: Other: grant; Shire: Consultancy, Speakers Bureau; Ablynx: Consultancy, Speakers Bureau; Federal Office of Public Health: Consultancy; Insel Gruppe AG: Current Employment. Friedman: Bayer: Consultancy; Alexion: Speakers Bureau; Siemens: Consultancy; Genentech: Consultancy; Sanofi: Consultancy; Instrumentation Laboratories: Consultancy.

An ADAMTS13 mutation that causes hereditary thrombotic thrombocytopenic purpura: a case report and literature review

BackgroundMutations in the ADAMTS13 gene can lead to an ADAMTS13 enzyme deficiency, which is related to Upshaw–Schulman syndrome (USS). USS is a common type of thrombotic thrombocytopenic purpura (TTP). Here we present a very rare case of TTP caused by 2 mutations in the ADAMTS13 gene. Besides, we reviewed and summarized previous pathogenic ADAMTS13 gene mutations associated with the TTP.Case presentationA 10-year-old female was admitted to the Third Xiangya Hospital of Central South University after experiencing discontinuous thrombocytopenia for 8 years, abnormal renal function for more than 2 years, cough for more than 10 days, and weakness of the left limb for 3 days. Gene sequencing shows the patient’s ADAMTS13 gene contains compound heterozygous nucleotide variations: c.1335delC (p. Phe445LeufsTer52) is a frameshift variation inherited from her father and c.2130C > G (p. Cys710Trp) is a missense variation inherited from her mother. The final diagnosis was USS.ConclusionsOur study reports a very rare genetic TTP case caused by two compound heterozygous variants in the ADAMTS13 gene. The effect of these two mutations on the secretion of ADAMTS13 requires further in vitro experiments to confirm.

ACUTE SPINAL CORD INFARCTION IN THE SETTING OF HEREDITARY THROMBOTIC THROMBOCYTOPENIC PURPURA

TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: Thrombotic thrombocytopenic purpura (TTP) is an acquired or inherited condition characterized by platelet aggregation and thrombosis due to an accumulation of von Willebrand factor multimers caused by decreased ADAMTS13 protease activity. It usually presents with fever, microangiopathic hemolytic anemia, thrombocytopenia, neurologic findings, and renal dysfunction. Acquired TTP is due to an inhibitory autoantibody against ADAMTS13 and is treated with glucocorticoids, rituximab, plasmapheresis, and caplacizumab [1]. Hereditary TTP is due to an autosomal recessive ADAMTS13 mutation and is treated with prophylactic and therapeutic plasma infusion [2]. Despite its prothrombotic nature, active bleeding at presentation is an uncommon complication described in literature. [3] We present an unusual case of hereditary TTP that caused acute spinal cord infarction from active bleeding into the spinal canal. CASE PRESENTATION: A 33-year-old female with past medical history of systemic lupus erythematosus presented with malaise, fevers, dyspnea, vomiting, and diarrhea. She was altered and febrile upon arrival, but then developed bleeding from the vagina, rectum, and bladder. TTP was empirically diagnosed based on fever, encephalopathy, and lab work (hemolysis, kidney injury, and thrombocytopenia). Blood product transfusions and plasmapheresis were initiated. Hereditary TTP was diagnosed based on decreased ADAMTS13 activity with negative inhibitor testing, so plasma infusions were started in lieu of plasmapheresis. During her hospitalization she exhibited progressive diffuse lower extremity weakness, sensory deficits, and absent deep tendon reflexes. MRI of the brain and spinal cord showed an infarction from C5 to the conus medullaris, as well as an extra-arachnoid fluid collection/hematoma throughout the dorsal canal from C3 to T12/L1. This was diagnosed as a subdural hematoma causing severe stenosis of the proximal and mid-thoracic canal. She was not a surgical candidate, so she was treated with plasma infusions and aggressive physical therapy. DISCUSSION: This case was challenging as TTP typically leads to thrombosis rather than bleeding, and the development of a spinal cord infarction is an unusual manifestation for TTP. Despite normal coagulation studies and negative active lupus studies, the patient's clinical presentation and decreased ADAMTS13 activity confirmed TTP even in the setting of significant bleeding. With acute spinal cord dysfunction, differential includes transverse myelitis, epidural abscess, infarction, and syringomyelia. MRI of the spine is diagnostic. TTP management must include platelet transfusion in the setting of active bleeding as it can be life saving.[3] CONCLUSIONS: TTP management differs on whether it is inherited or acquired. Although TTP is usually a prothrombotic entity, clinicians must keep it in the differential for active bleeding in the critically ill patient. REFERENCE #1: Scully M, Hunt BJ, Benjamin S, et al. Guidelines on the diagnosis and management of thrombotic thrombocytopenic purpura and other thrombotic microangiopathies. Br J Haematol 2012; 158:323. REFERENCE #2: Hamroun A, Prouteau C, Provôt F. Hereditary Thrombotic Thrombocytopenic Purpura. N Engl J Med 2020; 382:392. REFERENCE #3: Swisher KK, Terrell DR, Vesely SK, et al. Clinical outcomes after platelet transfusions in patients with thrombotic thrombocytopenic purpura. Transfusion 2009; 49:873. DISCLOSURES: No relevant relationships by Mohamed Hajmurad, source=Web Response No relevant relationships by Jonathan Hendrie, source=Web Response No relevant relationships by Hamza Khan, source=Web Response No relevant relationships by Daniel Matthews, source=Web Response

ADAMTS13 testing update: Focus on laboratory aspects of difficult thrombotic thrombocytopenic purpura diagnoses and effects of new therapies

AbstractTTP is a life‐threatening disorder diagnosed using a combination of clinical information and laboratory results. ADAMTS13 activity and antibody testing represent a major advance in the field, but results can sometimes be difficult to interpret due to technical aspects of the tests and characteristics of the causative antibodies in acquired TTP. Genetic testing for ADAMTS13 mutations is also now available to assist with the diagnosis of inherited TTP. This review will focus on ADAMTS13 testing and will highlight patient and laboratory aspects that can lead to diagnostic difficulty. The effects of TTP therapies on test results will also be discussed.

Frequency and Severity of Pregnancy Complications in Women with Hereditary Thrombotic Thrombocytopenic Purpura

Critical complications of pregnancy in women with hereditary thrombotic thrombocytopenic purpura (TTP) have been recognized since hereditary TTP was first described and they continue to be frequently reported. However, the frequency of complications, their severity, and when they occur during pregnancy are not known. We reviewed all case reports of patients with hereditary TTP whose diagnosis was confirmed by documentation of ADAMTS13 activity &amp;lt;10% and biallelic ADAMTS13 mutations. We identified 80 articles (180 patients) by searching MEDLINE and PubMed from 2001-March, 2020. 44 women were pregnant preceding their diagnosis of hereditary TTP; 9 had insufficient data for analysis. The remaining 35 women had 61 pregnancies (2 with twins). Major complications were defined as life-threatening, requiring urgent hospitalization. Other complications were defined as minor. 34 (97%) women had severe complications during one or more pregnancies (Table). 31 women had severe complications with their first pregnancy; 3 had spontaneous pregnancy losses at 5-11 weeks' gestation and then severe complications with their second pregnancy. Of the 31 women who had severe complications during their first pregnancy, 21 had no report of a subsequent pregnancy. 49 (84%) of the 58 pregnancies (excluding 3 pregnancies with elective induced termination) had severe complications. Gestational age was reported for 41 (84%) of the 49 pregnancies with severe complications; they occurred from 7 to 37 weeks' gestation (median, 23 weeks). 12 (29%) occurred at &amp;lt;20 weeks' gestation, when preeclampsia rarely occurs; 7 (17%) occurred in the first trimester. Among the 49 pregnancies with severe complications, outcome was reported for 48 infants; 16 (33%) survived. In 22 patients, pregnancy complications may have been the initial symptoms of hereditary TTP. Only 3 women had uncomplicated pregnancies, each following an initial pregnancy with severe complications; 2 women (2 pregnancies) were treated with aspirin throughout their pregnancy. 2 (6%) of the 34 women died from severe complications of their initial pregnancy. The risk of death with pregnancy may be greater than 6% because in 4 of the 29 families, an older sister had died from pregnancy complications but TTP was not suspected, ADAMTS13 activity was not measured. If these 4 women had been documented to have hereditary TTP, the frequency of deaths during pregnancy would have been 17%. The severe complications had the typical clinical features of TTP: thrombocytopenia, microangiopathic hemolytic anemia (MAHA); their symptoms were similar to features of severe preeclampsia. The diagnosis of TTP should be considered and ADAMTS13 activity measured in all women who have unusually severe or atypical preeclampsia. When TTP is diagnosed during pregnancy, both hereditary and acquired TTP should be considered. When hereditary TTP is diagnosed, plasma prophylaxis is required for all subsequent pregnancies. We begin plasma prophylaxis as soon as pregnancy is documented, adjusting the amount and interval to maintain the patient's normal platelet count; we continue plasma prophylaxis for 6 weeks postpartum. Prophylactic plasma can prevent exacerbations of TTP but it does not prevent the occurrence of preeclampsia. Figure Disclosures No relevant conflicts of interest to declare.

The quest for substrates and binding partners: A critical barrier for understanding the role of ADAMTS proteases in musculoskeletal development and disease.

Secreted ADAMTS metalloproteases are involved in the sculpting, remodeling, and erosion of connective tissues throughout the body, including in the musculoskeletal system. ADAMTS proteases contribute to musculoskeletal development, pathological tissue destruction, and are mutated in congenital musculoskeletal disorders. Examples include versican cleavage by ADAMTS9 which is required for interdigital web regression during limb development, ADAMTS5-mediated aggrecan degradation in osteoarthritis resulting in joint erosion, and mutations in ADAMTS10 or ADAMTS17 that cause Weill-Marchesani syndrome, a short stature syndrome with bone, joint, muscle, cardiac, and eye involvement. Since the function of ADAMTS proteases and proteases in general is primarily defined by the molecular consequences of proteolysis of their respective substrates, it is paramount to identify all physiological substrates for each individual ADAMTS protease. Here, we review the current knowledge of ADAMTS proteases and their involvement in musculoskeletal development and disease, focusing on some of their known physiological substrates and the consequences of substrate cleavage. We further emphasize the critical need for the identification and validation of novel ADAMTS substrates and binding partners by describing the principles of mass spectrometry-based approaches and by emphasizing strategies that need to be considered for validating the physiological relevance for ADAMTS-mediated proteolysis of novel putative substrates.

The ADAMTS/Fibrillin Connection: Insights into the Biological Functions of ADAMTS10 and ADAMTS17 and Their Respective Sister Proteases.

Secreted a disintegrin-like and metalloprotease with thrombospondin type 1 motif (ADAMTS) proteases play crucial roles in tissue development and homeostasis. The biological and pathological functions of ADAMTS proteases are determined broadly by their respective substrates and their interactions with proteins in the pericellular and extracellular matrix. For some ADAMTS proteases, substrates have been identified and substrate cleavage has been implicated in tissue development and in disease. For other ADAMTS proteases, substrates were discovered in vitro, but the role of these proteases and the consequences of substrate cleavage in vivo remains to be established. Mutations in ADAMTS10 and ADAMTS17 cause Weill–Marchesani syndrome (WMS), a congenital syndromic disorder that affects the musculoskeletal system (short stature, pseudomuscular build, tight skin), the eyes (lens dislocation), and the heart (heart valve abnormalities). WMS can also be caused by mutations in fibrillin-1 (FBN1), which suggests that ADAMTS10 and ADAMTS17 cooperate with fibrillin-1 in a common biological pathway during tissue development and homeostasis. Here, we compare and contrast the biochemical properties of ADAMTS10 and ADAMTS17 and we summarize recent findings indicating potential biological functions in connection with fibrillin microfibrils. We also compare ADAMTS10 and ADAMTS17 with their respective sister proteases, ADAMTS6 and ADAMTS19; both were recently linked to human disorders distinct from WMS. Finally, we propose a model for the interactions and roles of these four ADAMTS proteases in the extracellular matrix.

Two novel mutations in ADAMTS13 in a Chinese boy with congenital thrombocytopenic purpura: a case report

BackgroundMutations in the ADAMTS13 gene family have been reported to cause congenital thrombotic thrombocytopenic purpura (cTTP), a rare disease characterized by thrombocytopenia and hemolytic anemia. Nearly 150 causative mutations in ADAMTS13 have been identified; however, only a few of them were detected in Chinese patients.Case presentationA 5-year-old Chinese boy presented with history of thrombocytopenic purpura, hemolytic anemia, and renal injury since the neonatal period. Gene analysis revealed two novel mutations in ADAMTS13: a missense mutation 332G > A (p:Gly111Glu) in exon4 and a nonsense mutation 3121C > T (p:Gln1041stop) in exon 24. Genetic analysis of his parents confirmed the heterozygous nature of the mutations.ConclusionWe report two novel mutations in ADAMTS13 (332G > A, 3121C > T) in a Chinese boy. These two mutations may lead to early onset of cTTP and severe symptoms.

Stroke and Myocardial Infarction (MI) in Hereditary Thrombotic Thrombocytopenic Purpura (HTTP): Similarities to Sickle Cell Anemia (SSA)

Two recent large case series of patients with HTTP (UK Registry, Blood 2019; 133:1644; International Registry [IR], Haematologica 2019; in press) have reported that stroke is common (UK 25%, IR 31%) and MI is uncommon (IR 4%, UK not reported). The UK case series reported that 5 (7%) patients died; deaths were not reported in the IR case series. No data were reported on the ages when stroke, MI or death occurred (Table 1). To learn individual patient data, we searched MEDLINE and PubMed and identified 76 case reports/series describing 159 patients. Articles were filtered by publication date from 2001, when HTTP was first defined, through April 2019, and needed to report individual patient data to be included. 5 additional articles that focused on occurrence of stroke were excluded; none focused on MI. HTTP was documented by ADAMTS13 activity &lt;10% and biallelic ADAMTS13 mutations in 152 patients; 7 siblings who had characteristic clinical features of TTP but who had died before the diagnosis of HTTP was documented were also included. Approximately 68 of the 159 patients were included in the IR report; none were included in the UK report. 111 (70%) of the 159 patients were reported because they had novel ADAMTS13 mutations; the 48 other patients were reported for clinical issues (e.g., pregnancy, delayed diagnosis, development of ADAMTS13 inhibitor). Because the objective of these reports was not to describe stroke or MI, we believe that they provide objective evidence for the occurrence and characteristics of stroke and MI. Table 1 describes our 159 patients and compares them to the UK and IR data. 43 (27%) of our 159 patients had a symptomatic stroke, occurring at ages 1 day-79 years (median age, 19 years); two were diagnosed on autopsy. Clinically silent strokes were not reported. 11 of these 43 patients were included in the IR report. 4 of the 43 patients had hemorrhagic strokes; the others were assumed to be ischemic. 4 patients had been receiving regular plasma prophylaxis. 35 (81%) strokes occurred before HTTP was diagnosed. In 2 patients, stroke occurred with neither thrombocytopenia nor anemia. Of the 43 patients with stroke, 13 had recurrent strokes. 9 patients with reported stroke had died at the time of the case report. Of the 34 surviving patients, 9 had residual neurological deficits. 5 (3%) patients had an MI, occurring at ages 2-50 years (median age, 20 years); none were included in the IR report. In 3 patients, MI was diagnosed on autopsy; 4 patients had a prior or concurrent stroke. 17 (11%) patients died at ages 2-79 years (median age, 22 years). The median age of the last follow-up evaluation was 24 years. Among the case reports, not all clinical data described in Table 1 were reported for each patient. The actual frequency of stroke, MI, and death may be greater because we assumed that if these events were not reported, they did not occur. The frequencies of stroke and MI in our case report data are similar to the frequencies reported by the UK and International Registries, supporting the validity of our data. Our data emphasize the risk for stroke and death at a young age, although follow-up to older ages was limited. Our data also confirm the observation of the IR report that MI is uncommon. The duration of survival of patients with HTTP remains unknown because of the limited duration of follow-up. Our data for stroke in HTTP patients are strikingly similar to data for stroke in patients with SSA. In both disorders stroke is common and occurs at a young age (Figure 1, SSA data are from Powars, Medicine 2005; 84:363). Among all 1056 SSA patients, 116 (11%) had an overt stroke (median age, 20 years); clinically silent strokes were not reported. Most patients with HTTP (77%) and SSA (75%) had their first stroke before age 30. In the 1056 SSA patients, MI was not reported. The pathogenesis of stroke in patients with HTTP and SSA may be similar: embolic (platelet-von Willebrand factor complexes in HTTP, sickle cell complexes in SSA) rather than atherosclerosis. In both disorders the efficacy of anti-platelet or anticoagulant agents to prevent recurrent stroke is uncertain. The lower frequency of MI in patients with HTTP and SSA suggests that the brain is more vulnerable to the infarction caused by these disorders. Our data from a collection of case reports must be confirmed by long-term follow-up of individual patients. Disclosures No relevant conflicts of interest to declare.

A novel ADAMTS17 variant that causes Weill-Marchesani syndrome 4 alters fibrillin-1 and collagen type I deposition in the extracellular matrix

Weill-Marchesani syndrome (WMS) is a rare genetic disorder that affects the musculoskeletal system, the eye, and the cardiovascular system. Individuals with WMS present with short stature, joint contractures, thick skin, microspherophakia, small and dislocated lenses, and cardiac valve anomalies. WMS can be caused by recessive mutations in ADAMTS10 (WMS 1), ADAMTS17 (WMS 4), or LTBP2 (WMS 3), or by dominant mutations in fibrillin-1 (FBN1) (WMS 2); all genes encode secreted extracellular matrix (ECM) proteins. Individuals with WMS 4 due to ADAMTS17 mutations appear to have less severe cardiac involvement and present predominantly with the musculoskeletal and ocular features of WMS. ADAMTS17 is a member of the ADAMTS family of secreted proteases and directly binds to fibrillins. Here we report a novel pathogenic variant in ADAMTS17 that causes WMS 4 in an individual with short stature, brachydactyly, and small, spherical, and dislocated lenses. We provide biochemical and cell biological insights in the pathomechanisms of WMS 4, which also suggest potential biological functions for ADAMTS17. We show that the variant in ADAMTS17 prevents its secretion and we found intracellular accumulation of fibrillin-1 and collagen type I in patient-derived skin fibroblasts. In accordance, transmission electron microscopy revealed elastic fiber abnormalities, decreased collagen fibril diameters, and intracellular collagen accumulation in the dermis of the proband. Together, the data indicate a possible role for ADAMTS17 in the secretion of fibrillin-1 and collagen type I or in their early assembly in the pericellular matrix or the ECM.

Glaucoma-causing ADAMTS17 mutations are also reproducibly associated with height in two domestic dog breeds: selection for short stature may have contributed to increased prevalence of glaucoma

BackgroundIn humans, ADAMTS17 mutations are known to cause Weill-Marchesani-like syndrome, which is characterised by lenticular myopia, ectopia lentis, glaucoma, spherophakia, and short stature. Breed-specific homozygous mutations in ADAMTS17 are associated with primary open angle glaucoma (POAG) in several dog breeds, including the Petit Basset Griffon Vendeen (PBGV) and Shar Pei (SP). We hypothesised that these mutations are associated with short stature in these breeds.MethodsTwo hundred thirty-three PBGV and 66 SP were genotyped for their breed-specific ADAMTS17 mutations. The height of each dog was measured at the withers. We used linear (per allele) regression to assess the association between ADAMTS17 mutations and height as a continuous variable, and linear regression and likelihood ratio tests to assess the shape of the association by comparing a general model with a linear (per allele) model.ResultsThe adjusted mean heights of affected, carrier, and clear PBGV were 33.49 cm (n = 21, 95% CI 32.78–34.19 cm), 34.88 cm (n = 85, 95% CI 34.53–35.25 cm), and 34.92 cm (n = 121, 95% CI 34.62–35.21 cm), respectively. The mean heights of affected, carrier, and clear SP were 43.96 cm (n = 9, 95% CI 41.88–46.03 cm), 47.56 cm (n = 28, 95% CI 45.50–48.63 cm), and 48.95 cm (n = 23, 95% CI 47.80–50.11 cm), respectively. There was a significant difference between the height of affected and clear animals in the PBGV (P = 0.001) and the SP (P = < 0.0001).ConclusionsADAMTS17 POAG mutations are significantly associated with height in these breeds.