Congenital Thrombocytopenia Research Articles

Structural basis of MPL activation by thrombopoietin

AbstractMyeloproliferative leukemia protein (MPL), also known as thrombopoietin (TPO) receptor, is a class I cytokine receptor that is expressed on hematopoietic progenitors, promoting growth and differentiation toward the megakaryocyte lineage and is critical for normal platelet production. Mutations in MPL, TPO, or Janus kinase 2 (JAK2) have been implicated in multiple diseases from congenital thrombocytopenias to myeloproliferative neoplasms. The ligand for MPL, TPO, stimulates platelet production by inducing MPL dimerization and results in an active conformation that allows downstream JAK2/STAT5 signaling. Despite the biological importance of this pathway, the molecular signaling mechanism remained unclear. Here, we present a 3.39-Å cryo-electron microscopy structure of the ectodomain of mouse MPL bound to TPO. The structure revealed both low and high affinity sites between MPL and TPO that contain several pathologic mutations. To better understand TPO-driven MPL signaling, we expanded upon this structure by molecular dynamic (MD) simulations to model the full-length human MPL/TPO complex, and showed that MPL D4-D4 domain interactions are functionally relevant in activity assays. To build on our understanding of downstream activation, we added JAK2 to the MPL/TPO complex by MD simulations. This ternary complex illustrates JAK2 dimerization through the pseudokinase domain, illustrates residues important for MPL interactions, and reveals the constitutive activation mechanism of patient mutant V617F. The model also suggests the mechanism of JAK2 tyrosine kinase domain transphosphorylation. Overall, our studies illuminate TPO/MPL/JAK2 signaling mechanisms and provide additional insight into the nature of receptor signaling, which will further benefit human health.

Novel Mutation in ITGB3: A Case Report of Glanzmann Thrombasthenia-like Syndrome Associated with Macrothrombocytopenia

Abstract Congenital thrombocytopenias are a diverse range of diseases. Of them, Glanzmann thrombasthenia is an autosomal recessive platelet aggregation disorder due to defect in the alpha IIb/beta3 integrins, coded by the ITGA2B and ITGB3 genes. While most patients with mutations in the ITGA2B and ITGB3 genes typically exhibit normal platelet size and count, there are some rare and novel variants in these genes that can lead to an autosomal dominant form of macrothrombocytopenia (large platelets) accompanied by platelet functional defects. These cases have been collectively referred to as Glanzmann thrombasthenia-like syndrome (GTLS). We report a 12-year-old male presenting with mild bleeding symptoms and macrothrombocytopenia, who was diagnosed with GTLS and macrothrombocytopenia, also known as platelet-type bleeding disorder-24, caused by a novel heterozygous variant of the ITBG3 gene.

Diagnostic delay of MYH9-related disorder in Japan.

MYH9-related disorder (MYH9-RD) is characterized by congenital macrothrombocytopenia and granulocyte inclusion bodies. MYH9-RD is often misdiagnosed as chronic immune thrombocytopenia. In this study, we investigated age at definitive diagnosis and indicative thrombocytopenia in 41 patients with MYH9-RD from the congenital thrombocytopenia registry in Japan. Our cohort comprises 54.8% adults over 18 years at confirmed diagnosis. We found a significant difference (p < 0.0001) between the median age at definitive diagnosis of 25.0 years and for indicative thrombocytopenia it was 9.0 years. Our findings strongly suggest diagnostic delay of MYH9-RD in Japan. Our registry system will continue to contribute to this issue.

Heterozygous ITGA2B Phe1024 Deletion Associated with Abnormal αIIbβ3 Function in a Patient with Congenital Thrombocytopenia.

Heterozygous ITGA2B Phe1024 Deletion Associated with Abnormal αIIbβ3 Function in a Patient with Congenital Thrombocytopenia.

A novel missense mutation in the MECOM gene in a Chinese boy with radioulnar synostosis with amegakaryocytic thrombocytopenia

Radioulnar synostosis with amegakaryocytic thrombocytopenia (RUSAT) type 2, caused by MDS1 and EVI1 complex locus (MECOM) gene mutations, is a rare inherited bone marrow failure syndrome (IBMFS) with skeletal anomalies, characterized by varying presentation of congenital thrombocytopenia (progressing to pancytopenia), bilateral proximal radioulnar synostosis, and other skeletal abnormalities. Due to limited knowledge and heterogenous manifestations, clinical diagnosis of the disease is challenging. Here we reported a novel MECOM mutation in a Chinese boy with typical clinical features for RUSAT-2. Trio-based whole exome sequencing of buccal swab revealed a novel heterozygous missense mutation in exon 11 of the MECOM gene (chr3:168818673; NM_001105078.3:c.2285G > A). The results strongly suggest that the variant was a germline mutation and disease-causing mutation. The patient received matched unrelated donor hematopoetic stem cell transplantation (HSCT). This finding was not only expanded the pathogenic mutation spectrum of MECOM gene, but also provided key information for clinical diagnosis and treatment of RUSAT-2.

Inborn errors of immunity with kidney and urinary tract disorders: a review.

Human inborn errors of immunity (IEIs), previously referred to as primary immunodeficiency disorders (PIDs), are a heterogeneous spectrum of inherited abnormalities of the immune system with different organ involvement. The number of identified IEIs is rapidly increasing, highlighting the non-negligible role of an interdisciplinary approach in clinical diagnosis. Kidney disorders are one of the important comorbidities in some of the affected patients and play a significant role in the diagnosis and course of disease. According to recent studies, 22 types of human IEI with renal manifestations have been identified so far, including immunodeficiency with congenital thrombocytopenia, thymic defects with additional congenital anomalies, complement deficiencies, type 1 interferonopathies, immunity related to non-hematopoietic tissues, congenital neutropenia's, common variable immunodeficiency disorder (CVID) phenotype and immuno-osseous dysplasia. Based on this classification, we herein review IEIs with renal features and explain the genetic defect, inheritance, and type of renal manifestations.

Aberrant Activity of the Calcium Sensor STIM1 Underlies Congenital Platelet Disorders and Myeloproliferative Neoplasms

MB and VA equal contributors AB and STO co-corresponding authors This study was initiated following evaluation of a 32 year-old woman who presented with a history of thrombocytopenia identified in childhood who subsequently developed features of myelofibrosis (MF). A bone marrow biopsy demonstrated hypercellularity in conjunction with megakaryocyte hyperplasia and marked reticulin fibrosis. Molecular testing for JAK2, CALR, and MPL mutations was negative. Given the unusual association between congenital thrombocytopenia and MF in this patient, exome sequencing was performed, revealing a heterozygous R304W mutation in the coiled coil (CC) domain of STIM1. Activating mutations in the CC and EF hand domains of STIM1 have been associated with Stormorken syndrome, a rare congenital platelet disorder associated with abnormal store operated calcium entry (SOCE). We subsequently identified a second patient with MF associated with a STIM1 activating mutation. This individual was found to have severe thrombocytopenia at birth, and exome sequencing revealed a heterozygous S88G mutation in the EF hand of STIM1. A bone marrow biopsy obtained at 6 months of age revealed atypical megakaryocytes and grade 1-2 MF. A repeat biopsy at age 2 showed persistence of stable MF. The unusual finding of MF in these two patients suggested the possibility of altered calcium signaling as a shared mechanism driving congenital platelet disorders such as Stormorken syndrome and myeloproliferative neoplasms (MPNs) including MF. In support of this notion, we identified elevated STIM1 expression in MF vs normal megakaryocyte progenitors, as well as in platelets from patients with essential thrombocythemia (ET) vs healthy controls. Additionally, we found that STIM1 expression was significantly elevated in CD34+ hematopoietic stem/progenitor cells (HSPCs) from both ET and MF patients vs healthy controls. Notably, STIM1 expression was increased in both JAK2 and CALR-mutant MF patients. Collectively, these findings provide evidence of aberrant STIM1 expression in MPN patient cells. To determine the functional role of STIM1 in MPN disease development, colony assays and patient-derived xenograft (PDX) experiments were performed with MF patient CD34+ cells subjected to CRISPR ablation of STIM1. Strikingly discordant results were observed with JAK2 vs CALR-mutant patient samples. Abrogation of STIM1 in CALR-mutant CD34+ cells led to decreased colony formation, and NSGS mice engrafted in parallel with STIM1-targeted cells exhibited decreased human CD45+ cell engraftment in conjunction with prolonged survival. These findings suggest an important role for STIM1 in CALR-mutant MPN disease phenotypes. In contrast, targeting of STIM1 in JAK2-mutant CD34+ cells led to increased colony formation and exacerbated disease phenotypes in vivo as manifested by enhanced human CD45+ cell engraftment, worsened splenomegaly, and early lethality. Similar results were obtained in experiments utilizing pharmacologic inhibitors of SOCE activity. Taken together, these findings indicate that the consequences of aberrant STIM1 activity may be context-dependent relating to specific MPN driver mutations. To expand these observations, we identified a separate cohort of 9 family members in Italy with Stormorken syndrome and confirmed STIM1 EF hand mutations. In ex vivo megakaryocytic differentiation assays, cells from affected individuals exhibited a defect in proplatelet formation. These observations were corroborated by initial analyses of a newly generated Stim1 R304W conditional knock-in mouse which recapitulated the characteristic thrombocytopenia found in patients with Stormorken syndrome. In summary, this study represents the first demonstration of MF development in patients with Stormorken syndrome, thereby uncovering a previously unrecognized hallmark of altered calcium signaling via aberrant STIM1 activation underlying Stormorken syndrome and MPNs. Our findings suggest distinct mechanisms relating to the interaction between JAK2 vs CALR mutation and altered STIM1 activity. Further studies of these relationships may have important ramifications for potential therapeutic approaches targeting these pathways.

Treatment and Follow-up Data for Young Patients with a Gne Defect and Congenital Thrombocytopenia

Congenital thrombocytopenia can be associated not only with a reduced production, but also with an accelerated degradation of platelets. Sialic acid binds to platelet surface glycoproteins and protects platelets from degradation via the Ashwell-Morell receptor. The GNE gene encodes an enzyme that initiates and regulates the biosynthesis of N-acetylneuraminic acid, a precursor of sialic acids. According to OMIM alterations in GNE are autosomal recessive associated with adult-onset progressive GNE myopathy (with or without thrombocytopenia) and autosomal dominant with sialuria. In recent years, biallelic GNE mutations located mainly in the N-acetylmannosamine (ManNAc) kinase domain of GNE have been described in children/young adults with otherwise unexplained thrombocytopenia. Recently, we identified compound heterozygous GNE variants in a young girl (Pt.1) with life-threatening intracranial bleeding and severe congenital thrombocytopenia (lowest platelet count 5 x 10 9/L), who needed weekly platelet transfusions. We showed decreased α2,3 sialic acid and increased terminal galactose and α2,6 sialic acid moieties in the girl´s platelets. She received hematopoietic stem cell transplantation (HSCT) at 2,3 years, which normalized platelet counts and function. Follow-up data showed normalized platelet function (20 months after HSCT) and counts (20, 21, and 23 months after HSCT). Following HSCT, the platelet lectin profile was markedly different from before transplantation with an increase in α2,3 sialic acid recognizing lectins WGA and MAL I compared with data before transplantation, indicating that sialic acid moieties have been normalized. Additionally, we identified a biallelic GNE variant in two siblings (Pt.2 and Pt.3) affected by congenital thrombocytopenia. Pt.2 is a 1,8-year-old boy with thrombocytopenia since birth (lowest platelet count 6 x10 9/L) who needed weekly platelet transfusions. His 17-year-old sister (Pt.3) presented with lifelong thrombocytopenia and suspected chronic immune thrombocytopenia; however, therapy with immunoglobulin and steroids did not elevate the platelets. The parents and two other siblings were clinically not affected. Flow cytometry performed for the affected siblings showed severely decreased thrombin-induced platelet CD62 and CD63 exposure hinting at an impaired α- and δ-granule secretion. NGS identified a homozygous GNE variant (NM_001128227.3:c.1727G&amp;gt;C, p.Gly576Ala) with damaging prediction to be present in both siblings. The parents and two healthy siblings are heterozygous carriers of this variant. The nucleotide change c.1726G&amp;gt;C leading to Gly576Arg has been described compound heterozygous in a patient with GNE myopathy. For the sister (Pt.3) lectin binding analysis showed decreased α-2,3 sialylation (MAA) and increased terminal galactose (RCA120) expression on platelets. This pattern is consistent with loss of sialic acid synthesis and indicative of rapid platelet clearance. She had received therapy with romiplostim since she was 12, resulting in stable platelet counts (&amp;gt; 50 x10 9/L). At the age of 1 year, Pt.2 also started with romiplostim therapy. During the 8-month treatment, platelet counts were mainly stable above 30 x 10 9/L. Only two transfusions were necessary when platelet counts dropped to 18 and 11 x 10 9/L. In conclusion, this research elucidates novel associations between GNE mutations, specifically within the ManNAc kinase domain, and congenital thrombocytopenia. These findings were derived from studying three patients carrying such mutations, underscoring this discovery's potential broad relevance. Importantly, this alteration in the GNE gene, traditionally associated with GNE myopathy, prompts us to anticipate and closely monitor the potential future development of this neuromuscular condition in these patients. Of particular interest is the effectiveness of romiplostim in ameliorating thrombocytopenia in these cases. Both siblings in our study exhibited stable, acceptable platelet counts in response to this therapy, suggesting that romiplostim might offer a promising therapeutic strategy for managing congenital thrombocytopenia linked to GNE mutations.

Long-term follow-up of patients with congenital thrombotic thrombocytopenia purpura receiving a plasma-derived factor VIII (Koate) that contains ADAMTS13.

Hereditary thrombotic thrombocytopenia purpura (hTTP) is an ultra-rare disorder resulting from an inherited deficiency of ADAMTS13, a von Willebrand factor (VWF)-cleaving metalloprotease. The plasma-derived factor VIII/VWF Koate (FVIII/VWFKoate ) has been shown to contain ADAMTS13, allowing for its use to treat hTTP at home by the patient/caregiver. Based on prior demonstration of safe and effective use of FVIII/VWFKoate in eight patients with hTTP, we conducted a retrospective study to gather additional data regarding the use of FVIII/VWFKoate for hTTP. This was a multicentre, retrospective, noninterventional chart review of patients who had received FVIII/VWFKoate for the management of hTTP. Data collected included demographics, medical history, relevant family history, past use and tolerability of fresh frozen plasma, and details regarding FVIII/VWFKoate therapy. The cohort included 11 patients (seven males, four females) with hTTP, ranging in age at study entry from 2 to 28years. The average duration of FVIII/VWFKoate therapy was 4.8years (range, 0.5-6.5years). Among nine patients using FVIII/VWFKoate as prophylaxis, the normalized annual rate of breakthrough TTP episodes ranged from 0.2 to 1.1 episodes/year. All nine patients who received FVIII/VWFKoate prophylaxis had thrombocytopenia recorded at baseline, while eight (88.9%) did not have thrombocytopenia after using FVIII/VWFKoate . There was one AE (unspecified) attributed to FVIII/VWFKoate . These data suggest that FVIII/VWFKoate is a safe and well-tolerated source of the missing ADAMTS13 enzyme in patients with hTTP, producing a marked reduction in thrombocytopenia prevalence, low frequency of TTP episodes, and with the added benefit of self- or caregiver-administration.

Adding to the evidence of gene-disease association of RAP1B and syndromic thrombocytopenia.

Syndromic constitutive thrombocytopenia encompasses a heterogeneous group of disorders characterised by quantitative and qualitative defects of platelets while featuring other malformations. Recently, heterozygous, de novo variants in RAP1B were reported in three cases of syndromic thrombocytopenia. Here, we report two additional, unrelated individuals identified retrospectively in our data repository with heterozygous variants in RAP1B: NM_001010942.2(RAP1B):c.35G>A, p.(Gly12Glu) (de novo) and NM_001010942.2(RAP1B):c.178G>A, p.(Gly60Arg). Both individuals had thrombocytopenia, as well as congenital malformations, and neurological, behavioural, and dysmorphic features, in line with previous reports. Our data supports the causal role of monoallelic RAP1B variants that disrupt RAP1B GTPase activity in syndromic congenital thrombocytopenia.

Evaluating the prevalence of inborn errors of immunity in adults with chronic immune thrombocytopenia or Evans syndrome

AbstractInborn errors of immunity (IEIs) are monogenic disorders that predispose patients to immune dysregulation, autoimmunity, and infection. Autoimmune cytopenias, such as immune thrombocytopenia (ITP) and Evans syndrome (a combination of ITP and autoimmune hemolytic anemia), are increasingly recognized phenotypes of IEI. Although recent findings suggest that IEIs may commonly underlie pediatric ITP and Evans syndrome, its prevalence in adult patients with these disorders remains undefined. This study sought to estimate the prevalence of underlying IEIs among adults with persistent or chronic ITP or Evans syndrome using a next-generation sequencing panel encompassing >370 genes implicated in IEIs. Forty-four subjects were enrolled from an outpatient adult hematology clinic at a tertiary referral center in the United States, with a median age of 49 years (range, 20-83). Fourteen subjects (31.8%) had secondary ITP, including 8 (18.2%) with Evans syndrome. No cases of IEI were identified despite a high representation of subjects with a personal history of autoimmunity (45.5%) and early onset of disease (median age at diagnosis of 40 years [range, 2-77]), including 20.5% who were initially diagnosed as children. Eight subjects (18.2%) were found to be carriers of pathogenic IEI variants, which, in their heterozygous state, are not disease-causing. One case of TUBB1-related congenital thrombocytopenia was identified. Although systematic screening for IEI has been proposed for pediatric patients with Evans syndrome, findings from this real-world study suggest that inclusion of genetic testing for IEI in the routine work-up of adults with ITP and Evans syndrome has a low diagnostic yield.

ARPC5 deficiency leads to severe early-onset systemic inflammation and mortality.

The Arp2/3 complex drives the formation of branched actin networks that are essential for many cellular processes. In humans, the ARPC5 subunit of the Arp2/3 complex is encoded by two paralogous genes (ARPC5 and ARPC5L) with 67% identity. Through whole-exome sequencing, we identified a biallelic ARPC5 frameshift variant in a female child who presented with recurrent infections, multiple congenital anomalies, diarrhea and thrombocytopenia, and suffered early demise from sepsis. Her consanguineous parents also had a previous child who died with similar clinical features. Using CRISPR/Cas9-mediated approaches, we demonstrate that loss of ARPC5 affects actin cytoskeleton organization and function in vitro. Homozygous Arpc5-/- mice do not survive past embryonic day 9 owing to developmental defects, including loss of the second pharyngeal arch, which contributes to craniofacial and heart development. Our results indicate that ARPC5 is important for both prenatal development and postnatal immune signaling, in a non-redundant manner with ARPC5L. Moreover, our observations add ARPC5 to the list of genes that should be considered when patients present with syndromic early-onset immunodeficiency, particularly if recessive inheritance is suspected.

A Rare Immunodeficiency As a Cause of Inflammatory Bowel Disease; ARPC1B Deficiency

Actin-related protein 2/3 complex subunit 1B (ARPC1B) is involved in the control of actin polymerization. Homozygous loss-of-function mutations in ARPC1B cause immunodeficiency 71 classified as the syndromic combined immunodeficiency with congenital thrombocytopenia. Here we describe two siblings presented with homozygous mutations in the ARPC1B gene. Patient 1, a 12-year-old male, presented with bloody diarrhea, vomiting, fever and eczema starting at the age of five months. GIS endoscopic examination was compatible with Chron’s Disease. He had repeated hospitalizations due to fever, bloody diarrhea, vomiting, pneumonia, asthma, and bronchiolitis. Physical examination was normal except for marked growth retardation. Complete blood count (CBC) revealed thrombocytopenia with normal MPV values, lymphopenia as well as eosinophilia. He had high Ig A, low Ig M, and normal Ig G and Ig E levels. In the lymphocyte subgroup analysis, CD3+, CD8+ T, CD 19+ B cell and RTE percentages were low, and CD21+38+ low B cell percentages were high. Lymphocyte proliferation and Treg cell analysis were normal compared to healthy controls. Patient 2, Patient 1’s three-year-old brother started to complain of vomiting, bloody diarrhea, and eczema when he was four days old. Colonoscopy was revelaed Crohn’s Disease. He had episodes of wheezing and repeated hospitalizations for bronchiolitis. Physical examination revealed growth retardation and severe eczema. CBC was normal except for intermittent leukocytosis and eosinophilia. He had high Ig A and Ig E, low Ig M, and normal Ig G levels. In lymphocyte subgroup analysis, CD3 + T cell, RTE, naive, and CSM B cell percentages were low, CD21+38+ low B and Exhausted Cd8+ T cell percentages were high. T cell proliferative response was significantly lower than that in healthy controls. Treg cell analysis was also found to be significantly lower.Homozygous splicing mutation in the ARPC1B gene was detected in the WGS analysis of the patients. They are preparing for hematopoietic stem cell transplantation.IBD is an important finding of immune dysregulation. Advances in next-generation gene sequencing are revealing the underlying immunodeficiencies of IBDs. ARPC1B identified in our patients is an example of this. Diagnosis of patients reduces mortality and morbidity by providing new treatment options.

Expanded phenotypic and hematologic abnormalities beyond bone marrow failure in MECOM-associated syndromes.

The MECOM gene encodes multiple protein isoforms that are essential for hematopoietic stem cell self-renewal and maintenance. Germline MECOM variants have been associated with congenital thrombocytopenia, radioulnar synostosis and bone marrow failure; however, the phenotypic spectrum of MECOM-associated syndromes continues to expand and novel pathogenic variants continue to be identified. We describe eight unrelated patients who add to the previously known phenotypes and genetic defects of MECOM-associated syndromes. As each subject presented with unique MECOM variants, the series failed to demonstrate clear genotype-to-phenotype correlation but may suggest a role for additional modifiers that affect gene expression and subsequent phenotype. Recognition of the expanded hematologic and non-hematologic clinical features allows for rapid molecular diagnosis, early identification of life-threatening complications, and improved genetic counseling for families. A centralized international publicly accessible database to share annotated MECOM variants would advance their clinical interpretation and provide a foundation to perform functional MECOM studies.

A Novel Likely Pathogenic Variant in the RUNX1 Gene as the Cause of Congenital Thrombocytopenia.

Heterozygous pathogenic and likely pathogenic sequence variants in the RUNX1 (Runt-related Transcription Factor 1) gene are a common genetic cause of decreased platelet count and/or platelet dysfunction and an increased risk of developing myelodysplasia and acute myeloid leukemia. The majority of causative variants are substitutions, which rarely occur de novo. The aim of this case report is to present a patient with congenital thrombocytopenia caused by a deletion variant in exon 9 in the RUNX1 gene. A one-month-old male infant was admitted to the Clinical Hospital Center Rijeka because of anemia and thrombocytopenia verified in the course of an acute viral infection. During follow-up, he occasionally had petechiae and ecchymoses on the lower extremities after mild trauma, with no other symptoms. The patient had persistent slightly decreased values of platelets with normal morphology, but with pathological aggregation with adrenaline and adenosine diphosphate. Due to the unclear etiology of persistent mild thrombocytopenia, he was referred for genetic testing at the age of five. Genomic DNA was isolated from the patient's peripheral blood and whole-exome sequencing was performed using the next-generation sequencing method. A heterozygous frameshift variant, c.1160delG (NM_001754.4), was identified in exon 9. The variant is classified as likely pathogenic. To the best of our knowledge, the heterozygous variant c.1160delG in the RUNX1 gene was first described in our patient. Although pathogenic variants in the RUNX1 genes are very rare, persistently low platelet counts of unclear etiology should raise suspicion of an underlying genetic disorder.

Congenital cytomegalovirus infection-related thrombocytopenia

Congenital cytomegalovirus infection-related thrombocytopenia

Severe congenital thrombocytopenia and platelet dysfunction due to novel WAS gene mutation: case report

Severe congenital thrombocytopenia and platelet dysfunction due to novel WAS gene mutation: case report

Long-Term Follow-up of Patients with Congenital Thrombotic Thrombocytopenia Purpura Receiving Plasma-Derived Factor VIII Containing (Koate®)

Background: Congenital thrombotic thrombocytopenia purpura (cTTP) is an ultra-rare disorder resulting from an inherited deficiency of ADAMTS13, a von Willebrand factor (VWF)-cleaving metalloprotease. Clinically, cTTP is characterized by recurring, and potentially life-threatening, episodes of VWF-platelet aggregation and microvascular thrombosis. Treatment has traditionally been replacement of ADAMTS13 using fresh frozen plasma (FFP) or solvent detergent treated plasma, options which are limited by risks of severe allergic reactions, viral exposure, and volume overload. The marketed plasma-derived factor VIII/VWF Koate® (hereafter, FVIII/VWFKoate) has been shown to have the highest concentration of ADAMTS13 among tested plasma-derived concentrates [Peyvandi F, et al. Am J Hematol. 2013;88:895-898] and can be administered by the patient or a caregiver in the patient's home. Based on a prior case series that reported safe and effective use of FVIII/VWFKoate in 8 patients with cTTP [Aledort LM, et al. J Pediatr Hematol Oncol 2017;39:524-527], we conducted a retrospective study to gather additional data regarding the use of FVIII/VWFKoate for this disease. Methods: This was a multi-center (United States, n=8 sites; Canada, n=1 site), retrospective, non-interventional chart review of patients who had received at least one dose of FVIII/VWFKoate for the management of cTTP between 8/1/2014 and 1/31/21 (through 12/31/21 at one center). Data collected included patient demographics, medical and family history relevant to cTTP, past use and tolerability of FFP, and details regarding FVIII/VWFKoate therapy, including dose, duration of therapy, TTP episodes, clinical and laboratory outcomes, adverse events (AEs), and reported difficulty with FVIII/VWFKoate administration. Results: The cohort included 11 patients (7 males, 4 females) with cTTP, ranging in age (at the time of data collection) from 2-28 years (Table 1). Age at diagnosis of cTTP ranged from 0 months to 15 years. Eight patients had at least one immediate family member with cTTP. Eight patients had been previously treated with FFP and 5 were noted to have experienced AEs including allergic reactions/rashes. The average duration of therapy with FVIII/VWFKoate was 4.8 years (range, 0.5-6.5 years). Individual FVIII/VWFKoate doses ranged from 1000-3700 IU per dose. Nine patients used FVIII/VWFKoate regularly as prophylaxis; dosing frequencies at the time of data collection included weekly (n=5), twice weekly (n=2), 3 times/week (n=1), and every 2 weeks (n=1). Two patients used FVIII/VWFKoate only as needed. Doses were administered by the patient/caregiver (n=9) or by a nurse (n=2). Among the 9 patients using FVIII/VWFKoate on an ongoing basis as prophylaxis, the normalized annual rate of breakthrough TTP episodes ranged from 0.2 to 1.1 episodes/year. There were no AEs attributed to FVIII/VWFKoate. At the time of cTTP diagnosis, 4 patients had microangiopathic hemolytic anemia, and 3 of the 4 did not have persistent anemia following treatment with FVIII/VWFKoate; 1 additional patient had persistent anemia considered unrelated to cTTP. Among 8 patients who used FVIII/VWFKoate as prophylaxis and who had baseline data regarding presence/absence of thrombocytopenia, all 8 had thrombocytopenia prior to FVIII/VWFKoate and 7 of the 8 (87.5%) did not have thrombocytopenia after using FVIII/VWFKoate (95% confidence interval, 46.7% to 99.3%). The 1 patient who had residual thrombocytopenia after using FVIII/VWFKoate had no recorded TTP episodes while using FVIII/VWFKoate. Renal impairment was noted in 1 patient at the time of diagnosis and 1 (different) patient following FVIII/VWFKoate treatment. None of the patients were noted to have evidence of residual CNS impairment at the time of diagnosis or following FVIII/VWFKoate treatment. Conclusions: These data, reflecting treatment periods averaging almost 5 years, suggest that FVIII/VWFKoate appears to be a safe and effective source of the missing ADAMTS13 enzyme in patients with cTTP, producing a marked reduction in prevalence of thrombocytopenia, low frequency of TTP episodes, and with the added benefit of self- or caregiver-administration. Regimens of FVIII/VWFKoate varied greatly in this real-world study, and additional experience is needed to optimize dosing recommendations for this rare disease. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Immune Thrombocytopenia Purpura Relapse in Patients Who Received mRNA COVID-19 Vaccines

Background: Immune thrombocytopenic purpura (ITP) is a syndrome in which platelets become coated with autoantibodies to platelet membrane antigens. The mononuclear macrophage system of the spleen is responsible for removing platelets in ITP. This leads to a decrease in circulating platelet count and propensity for bleeding. Patients usually present with bruising and mucosal bleeding, with a minority of cases developing major bleeding complications such as intracranial hemorrhage. Cases of ITP and ITP relapse have been reported in people who received the mRNA SARS-CoV-2 vaccine, most reported cases present with bruising and mucosal bleeding in the first few weeks after receiving the vaccine, nevertheless, the causal relationship is not yet proved. Objectives: This study aims to prove the causal relationship betweenITP relapse in known ITP patients and the mRNA covid vaccine. And to evaluate the long-term effect of the vaccine on ITP patients > 6 months after receiving the second dose. Methods a retrospective study was conducted to check platelet count in 67 patients known for immune thrombocytopenia purpura, who are >18-year- old, and not known for any other causes of thrombocytopenia (including congenital thrombocytopenia, malignancy, SLE, anti-phospholipid syndrome). The platelet count was identified at baseline before receiving the vaccine and within 3 months, 6 months, and after 6 months after receiving the vaccine. Results: The results showed that 6% of ITP patients had ITP relapse within the first 3 months after the mRNA covid vaccine, 10% of patients had a relapse within the first 6 months and another 8% had a relapse more than 6 months after receiving the vaccine. on follow-up for the patient who didn't have a frank relapse, within the first 6 months after receiving the vaccine 8% of patients had more than 50% reduction from their baseline platelet count and 6% had a 25-50% reduction in the platelets count. on follow-up more than 6 months after the vaccine,4% of patients had more than 50% reduction in platelet count and 3% had a 25-50% reduction from their baseline platelet count. There was no statically significant difference between Moderna and Pfizer vaccine on ITP relapse rate or platelet count reduction. Conclusion mRNA covid vaccine increases the risk of ITP relapse and leads to a reduction in platelets count compared to the baseline count before receiving the vaccine, with no statically significant difference between Pfizer and Moderna vaccines. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

THROMBOCYTOPENIA, HYPOGAMMAGLOBULINEMIA, AND POOR VACCINE RESPONSE IN A PATIENT WITH TAKENOUCHI-KOSAKI SYNDROME

<h3>Introduction</h3> Takenouchi-Kosaki Syndrome (TKS) is a rare congenital developmental disorder characterized by thrombocytopenia, facial abnormalities, and varied multisystemic anomalies including immunodeficiency. Heterozygous deficiency of CDC42, an intracellular signaling GTPase, has been found in all TKS patients described to date. The immunological phenotypes of TKS patients are heterogeneous: recurrent infections have been noted in some patient series but with variable penetrance. Herein we describe a case of TKS causing hypogammaglobulinemia, B-cell lymphopenia, and poor vaccine response. <h3>Case Description</h3> A fifteen-year-old girl with history of developmental delay, multiple congenital defects, and lymphedema was referred to the immunology clinic for evaluation of recurrent ear infections that began at 3 months of age requiring tympanostomy tube placement at 18 months. Her physical exam was notable for abnormal facies, scoliosis, strabismus, abnormal thumbs, and unilateral lymphedema. Her laboratory evaluation revealed macrothrombocytopenia, mild leukopenia with low T-cells and markedly low B-cells by flow cytometry, and notably low IgA (11.7, RR 69 – 309) and IgG (423, RR 613 – 1295). She had a poor response to a full course of PCV7 with PPSV23 booster (9 of 23 > 1.3). Whole exome sequencing identified a heterozygous p.Y64C mutation in CDC42 consistent with TKS. <h3>Discussion</h3> The Y64C mutation in CDC42 is a TKS Group I lesion causing ineffective intracellular signaling, resulting in <i>in vitro</i> defects including abnormal cellular proliferation and disruption of cell polarity. Actin remodeling disorders such as Wiskott-Aldrich Syndrome and TKS should be considered in patients with immunodeficiency and congenital thrombocytopenia.