ANKRD26-related Thrombocytopenia Research Articles

Analysis of clinical characteristics and treatment efficacy in two pediatric cases of ANKRD26-related thrombocytopenia

ANKRD26-related thrombocytopenia (ANKRD26-RT or THC2, MIM 188 000), an autosomal dominant thrombocytopenia, is unresponsive to immunosuppressive therapy and susceptible to hematological malignancies. A large number of pediatric patients are diagnosed with immune thrombocytopenia (ITP) every year; however, thrombocytopenia of genetic origin is often missed. Extensive characterization of ANKRD26-RT will help prevent missed diagnosis and misdiagnosis. Furthermore, identification of ANKRD26-RT will help in the formulation of an accurate diagnosis and a treatment plan. In our study, we report cases of two Chinese pediatric patients with ANKRD26-RT and analyze their clinical characteristics, gene mutations, and treatment modalities. Both patients were 1-year-old and presented with mild bleeding (World Health Organization(WHO) score grade 1), different degrees of platelet reduction, normal mean platelet volume, and megakaryocyte maturation impairment not obvious. Genetic tests revealed that both patients had ANKRD26 gene mutations.Patient 1 had a mutation c.-140C>G of the 5’ untranslated region (UTR), and patient 2 had a mutation of c.-127A>T of 5’UTR. Both patients were treated with eltrombopag, and the treatment was no response, with no adverse reactions.

ANKRD26-Related Thrombocytopenia and Predisposition to Myeloid Neoplasms.

This review describes ANKRD26-related thrombocytopenia (RT) from a molecular, clinical, and laboratory perspective, with a focus on the clinical decision-making that takes place in the diagnosis and management of families with ANKRD26-RT. ANKRD26-related thrombocytopenia (ANKRD26-RT) is a non-syndromic autosomal dominant thrombocytopenia with predisposition to hematologic neoplasm. The clinical presentation is variable with moderate thrombocytopenia with normal platelet size and absent to mild bleeding being the hallmark which makes it difficult to distinguish from other inherited thrombocytopenias. The pathophysiology involves overexpression of ANKRD26 through loss of inhibitory control by transcription factors RUNX1 and FLI1. The great majority of disease-causing variants are in the 5' untranslated region. Acute myeloid leukemia, myelodysplastic syndrome, and chronic myelomonocytic leukemia have been reported to occur in the context of germline variants in ANKRD26, with the development of somatic driver mutations in hematopoietic regulators playing an important role in malignant transformation. In the absence of clear risk estimates of development of malignancy, optimal surveillance strategies and interventions to reduce risk of evolution to a myeloid disorder, multidisciplinary evaluation, with a strong genetic counseling framework is essential in the approach to these patients and their families. Gene-specific expertise and a multidisciplinary approach are important in the diagnosis and treatment of patients and families with ANKRD26-RT. These strategies help overcome the challenges faced by clinicians in the evaluation of individuals with a rare, non-syndromic, inherited disorder with predisposition to hematologic malignancy for which large data to guide decision-making is not available.

Prevalence and natural history of variants in the ANKRD26 gene: a short review and update of reported cases

ANKRD26 is a highly conserved gene located on chromosome 10p12.1 which has shown to play a role in normal megakaryocyte differentiation. ANKRD26-related thrombocytopenia, or thrombocytopenia 2, is an inherited thrombocytopenia with mild bleeding diathesis resulting from point mutations the 5ʹUTR of the ANKRD26 gene. Point mutations in the 5ʹUTR region have been shown to prevent transcription factor-mediated downregulation of ANKRD26 in normal megakaryocyte differentiation. Patients with ANKRD26-related thrombocytopenia have a predisposition to developing hematological malignancies, with acute myeloid leukemia and myelodysplastic syndrome most commonly described in the literature. We review the clinical features and biological mechanisms of ANKRD26-related thrombocytopenia and summarize known cases in the literature.

Platelet phenotype in children with ANKRD26-related thrombocytopenia

The mechanisms of hemorrhagic manifestations in patients with ANKRD26associated thrombocytopenia (ANKRD26-AT) are poorly understood. The aim of this work is to detect possible morpho-functional disorders of platelets in patients with mutations in the ANKRD26gene by flow cytometry with activation. The study was approved by the Independent Ethics Committee of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. 8 children aged from 1.5 to 15 years were examined. The platelet count ranged from 29 to 172 thousand/μl, with a median of 60 thousand/μl. The severity of hemorrhagic manifestations was assessed on a standardized scale (Pediatric Bleeding Questionnaire, PBQ) and it ranged from 0 to 5 points, with a median of 3.5 points. Platelet activation was performed with a CRP + TRAP mixture. Comparison was carried out with the results of examination of 26 apparently healthy children (control group, CG) aged 2 to 15 years. When compared with CG, patients showed an increase in platelet size (FSC; p= 0.018) and granularity (SSC; p< 0.001) after activation. In contrast to the CG, the correlation between FSC and SSC of platelets in patients was not significant (cor. = 0.55; p= 0.15). Patients showed a high, significant relationship between the number and FSC of platelets (cor. = –0.93; p< 0.001), as well as an increased density of CD42b (p < 0.001) and a decrease in the proportion of procoagulant platelets (p= 0.01) after activation. The revealed changes indicate violations of the mechanisms of activation and shape changes of platelets in patients with ANKRD26-AT.

Role of Thrombopoietin Receptor Agonists in Inherited Thrombocytopenia.

In the last decade, improvements in genetic testing have revolutionized the molecular diagnosis of inherited thrombocytopenias (ITs), increasing the spectrum of knowledge of these rare, complex and heterogeneous disorders. In contrast, the therapeutic management of ITs has not evolved in the same way. Platelet transfusions have been the gold standard treatment for a long time. Thrombopoietin receptor agonists (TPO-RA) were approved for immune thrombocytopenia (ITP) ten years ago and there is evidence for the use of TPO-RA not only in other forms of ITP, but also in ITs. We have reviewed in the literature the existing evidence on the role of TPO-RAs in ITs from 2010 to February 2021. A total of 24 articles have been included, 4 clinical trials, 3 case series and 17 case reports. A total of 126 patients with ITs have received TPO-RA. The main diagnoses were Wiskott–Aldrich syndrome, MYH9-related disorder and ANKRD26-related thrombocytopenia. Most patients were enrolled in clinical trials and were treated for short periods of time with TPO-RA as bridging therapies towards surgical interventions, or other specific approaches, such as hematopoietic stem cell transplantation. Here, we have carried out an updated and comprehensive review about the efficacy and safety of TPO-RA in ITs.

Relation between mutations in the 5′ UTR of ANKRD26 gene and inherited thrombocytopenia with predisposition to myeloid malignancies. An Egyptian study

Inherited thrombocytopenias are a heterogeneous group of diseases characterized by a reduced number of platelets and a bleeding tendency that ranges from very mild to life threatening especially in surgery. Mutations in the 5′ untranslated region (UTR) of Ankirin repeat domain 26 (ANKRD26) are responsible for autosomal-dominant form of thrombocytopenia, that is known as ANKRD26-related thrombocytopenia (ANKRD26 RT), characterized by a moderate thrombocytopenia with mild propensity to bleeding and predisposition to hematological malignancies including AML and MDS. We included 90 unrelated patients with inherited thrombocytopenia. In addition, we investigated 45 patients with ITP. Peripheral blood and bone marrow samples were collected and examined and molecular detection of mutations in the 5︡ UTR of ANKRD26 gene was performed for all the patients. Also, screening of the mutation and development of myeloid malignancies in the extended series of the affected subjects was done. ANKRD26 mutations were identified in 10% of the patients with inherited thrombocytopenia. The most common types were c.128 G > A and c.127A>T, while no mutations were found in the ITP group. In those affected, the median number of platelets was 69 x109/L (43–106) with normal MPV in most of the patients (9.4–11.6). There was a statistically significant increase in the unexpected high frequency of myeloid malignancies in the extended series of the mutated subjects compared with the ITP group-extended series (P < .001). So, we can conclude that ANKRD26 RT is associated with increased risk for developing myeloid malignancies and ANKRD26 mutations can represent a valuable tool for making therapeutic decisions.

ANKRD26 Coding Variants Presenting with Giant Platelets and a Predisposition to Myeloid Neoplasia

ANKRD26 Coding Variants Presenting with Giant Platelets and a Predisposition to Myeloid Neoplasia

Characterization of Pathogenic Variants Associated with Hereditary Thrombocytopenias in Families from the Czech Republic

Introduction Inherited thrombocytopenias (IT) are a heterogeneous group of 33 different forms of monogenic disorders caused by molecular defects affecting 40 genes at least. The pathogenic germline variants play an important role in the development and maintenance of hematopoietic system (megakaryopoesis and thrombopoesis). These changes lead to disruption of these processes and are presented as the thrombocytopenia phenotype (low platelet count, blood-examination). However, patients are occasionally misdiagnosed with the immune thrombocytopenia and unsuccessfully treated with steroid therapy and splenectomy. In some patients, accurate diagnosis of IT can only be established based on the results of molecular genetic testing. Furthermore, it has also been shown that some hematological conditions with Mendelian type of hereditability precede the development of hematooncological disease. Patients and Methods DNA samples from peripheral blood or buccal swabs of four unrelated families were isolated. The whole exome sequencing (WES) was performed using the NextSeq 500 Illumina instrument with adequate chemistry and sequencing libraries were prepared according to the SeqCap EZ Human Exome Probes v3 protocol. The generated data were processed using in-house bioinformatics pipelines. The detected pathogenic variants were confirmed by Sanger sequencing. Moreover, the novel variant was analyzed in silico using analytical procedures including protein modelling, too. Germline DNA analysis was performed on all available samples and somatic DNA analysis was done for the oncological patient. Within each family, the obtained pathogenic variants were compared between the individuals with IT phenotype and their disease-free relatives. Results The pathogenic variants were characterized in four families with different forms of IT. Moreover, the additional genetic variants were detected in three of them which predispose to the development of hematological malignancies. In the first family, a novel heterozygous variant c.320C&gt;T; p.(Thr107Met) in TUBB1 gene is probably responsible for essential thrombocytopenia disease because all rare TUBB1 variants until now have been detected in patients with macrothrombocytopenia. The known pathogenic variant c.1402G&gt;T; p.(Val468Phe) in JAK2 gene (10.9% frequency) was identified in a family member suffering from the myeloproliferative disease. In the second family, heterozygous pathogenic variants c.3076C&gt;T; p.(Arg1026Trp) in ITGA2B gene and c.3188G&gt;A; p.(Arg1063His) in JAK2 gene were detected, associated with platelet-type bleeding disorders and hereditary erythrocytosis with megakaryocytic atypia and predisposition for hematological malignancy, respectively. It is known that stomach tumor occurred in patient´s family before. In the third family, heterozygous pathogenic variant c.3493C&gt;T; p.(Arg1165Cys) in MYH9 gene was identified in a patient with macrothrombocytopenia. This variant was associated with Sebastian syndrome, macrothrombocytopenia and granulocyte inclusions and predisposition to kidney failure, hearing loss, and cataracts. In the fourth family, ANKRD26-related thrombocytopenia with predisposition to myeloid malignancy was probably identified in a patient with detected heterogeneous known variant c.-140C&gt;G in 5´ UTR of ANKRD26 gene. Moreover, the novel c.682C&gt;T; p.(Arg228Trp) variant in SYTL3 gene with uncertain significance was detected in this patient. Conclusions The pathogenic variants were detected in unrelated affected families with macrothrombocytopenia, platelet-type bleeding disorders and hereditary erythrocytosis with megakaryocytic atypia, Sebastian syndrome, and ANKRD26-related thrombocytopenia. Moreover, the genetic variants predispose to myeloid malignancy were identified. Molecular genetic testing helped the clinicians to determine the correct diagnosis in these patients. This study was supported by Ministry of Health of the Czech Republic (grant No 16-29447A), and TA CR (TE02000058). Disclosures No relevant conflicts of interest to declare.

ANKRD26-related thrombocytopenia: case report and literature review of inherited thrombocytopenias with predisposition to malignancies

ANKRD26-related thrombocytopenia (previously known as thrombocytopenia-2) is a rare form of inherited platelet disorders. Patients with ANKRD26-related thrombocytopenia usually do not suffer from severe bleeding but have predisposition to acute myeloid leukemia and other malignancies. Patients with ANKRD26-related thrombocytopenia and their relatives need genetic consultation and long term follow-up in view of risk of malignant blood disorders. The clinical case of ANKRD26-related thrombocytopenia in two siblings is presented in this paper. Review of literary data on pathogenesis, treatment and follow-up of patients with ANKRD26-related thrombocytopenia is performed. Common questions of diagnosis and management in patients with congenital thrombocytopenias with predisposition to malignant blood disorders are also reviewed. Parents gave their permission for using personal data for clinical research and publications.

PS1496 ANKRD26‐RELATED THROMBOCYTOPENIA: STUDY OF 3 FAMILIES

Background:ANKRD26‐related thrombocytopenia (ANKRD26‐RT) is a non‐syndromic form of inherited thrombocytopenia with autosomal dominant transmission, caused by mutations in the 5’UTR region of the ANKRD26 gene. About 8–10% of the patients develop myeloid neoplasms. Recently, in the 2016 revision of the WHO, this entity was recognized in the group of myeloid neoplasms with germ line predisposition and preexisting platelet disordersAims:Characterization of 3 portuguese families with ANKRD26‐RT.Methods:Study of 3 families with thrombocytopenia and ANKRD26 gene mutation. Initial study on NGS platform (Ion Torrent ™, Thermo Fisher Scientific), subsequent confirmation/family studies by Sanger direct sequencing. Clinical (symptoms, treatment, evolution) and laboratory data (platelets, MPV, Hb, leukocytes, bone marrow) were analyzed for 11 individuals.Results:Mutations in the 5’UTR region of the ANKRD26 gene in heterozygosity were found in 11 individuals studied, belonging to 3 families with autosomal dominal familial thrombocytopenia and normal MPV.: c.‐118C&gt;T mutation in family 1 and 2, and the more recently described c.‐140C&gt;G mutation in family 3. Median age at diagnosis of thrombocytopenia was 16 years (0.25–55), with a current median age of 36 years (2–73). In those affected, the median number of platelets is 48x109L (8–203), with persistently normal MPV in 82% of patients (8,2–12,9). In our cohort, the elderly (&gt; 65 years) had lower platelet counts (&lt;15x109L) and 1 family member with the c.‐140C&gt;G mutation had normal platelet count in one determination. About half of the patients had Htc&gt; 45% (max 50.4%). More than half of the patients (54.5%) were initially interpreted as ITP and treated with prednisolone or IV Ig, with no response. Only 5 patients experienced bleeding events, two requiring platelet transfusion. The patient with the most significant hemorrhagic symptoms (45 years old, platelets 15–30x109L) was classified as MDS in 2011.Summary/Conclusion:ANKRD26‐RT is associated with a risk of developing myeloid neoplasia, making its diagnosis and monitoring particularly important. The recognition of this entity is recent and probably underdiagnosed. In our center we identified 3 ANKRD26‐RT families, 2 of them had 3 affected generations. Its characterization and follow‐up will allow us to better understand the variability of presentation and evolution and possibly the identification of bio‐clinical risk factors for neoplastic transformation.

Ubiquitin/proteasome-rich particulate cytoplasmic structures (PaCSs) in the platelets and megakaryocytes of ANKRD26-related thrombocytopenia

ANKRD26-related thrombocytopenia (ANKRD26-RT) is an autosomal-dominant thrombocytopenia caused by mutations in the 5'UTR of the ANKRD26 gene. ANKRD26-RT is characterised by dysmegakaryopoiesis and an increased risk of leukaemia. PaCSs are novel particulate cytoplasmic structures with selective immunoreactivity for polyubiquitinated proteins and proteasome that have been detected in a number of solid cancers, in the epithelia of Helicobacter pylori gastritis and related preneoplastic lesions, and in the neutrophils of Schwachman-Diamond syndrome, a genetic disease with neutropenia and increased leukaemia risk. We searched for PaCSs in blood cells from 14 consecutive patients with ANKRD26-RT. Electron microscopy combined with immunogold staining for polyubiquitinated proteins, 20S and 19S proteasome showed PaCSs in most ANKRD26-RT platelets, as in a restricted minority of platelets from healthy controls and from subjects with other inherited or immune thrombocytopenias. In ANKRD26-RT platelets, the PaCS amount exceeded that of control platelets by a factor of 5 (p<0.0001). Immunoblotting showed that the higher PaCS number was associated with increased amounts of polyubiquitinated proteins and proteasome in ANKRD26-RT platelets. PaCSs were also extensively represented in ANKRD26-RT megakaryocytes, but not in healthy control megakaryocytes, and were absent in other ANKRD26-RT and control blood cells. Therefore, large amounts of PaCSs are a characteristic feature of ANKRD26-RT platelets and megakaryocytes, although these novel cell components are also present in a small subpopulation of normal platelets. The widespread presence of PaCSs in inherited diseases with increased leukaemia risk, as well as in solid neoplasms and their preneoplastic lesions, suggests a link of these structures with oncogenesis.

Inherited thrombocytopenias

The chapter of inherited thrombocytopenias has expanded greatly over the last decade and many "new" forms deriving from mutations in "new" genes have been identified. Nevertheless, nearly half of patients remain without a definite diagnosis because their illnesses have not yet been described. The diagnostic approach to these diseases can still take advantage of the algorithm proposed by the Italian Platelet Study Group in 2003, although an update is required to include the recently described disorders. So far, transfusions of platelet concentrates have represented the main tool for preventing or treating bleedings, while haematopoietic stem cell transplantation has been reserved for patients with very severe forms. However, recent disclosure that an oral thrombopoietin mimetic is effective in increasing platelet count in patients with MYH9-related thrombocytopenia opened new therapeutic perspectives. This review summarizes the general aspects of inherited thrombocytopenias and describes in more detail MYH9-related diseases (encompassing four thrombocytopenias previously recognized as separate diseases) and the recently described ANKRD26-related thrombocytopenia, which are among the most frequent forms of inherited thrombocytopenia.

Mutations in ANKRD26 are responsible for a frequent form of inherited thrombocytopenia: analysis of 78 patients from 21 families

AbstractUntil recently, thrombocytopenia 2 (THC2) was considered an exceedingly rare form of autosomal dominant thrombocytopenia and only 2 families were known. However, we recently identified mutations in the 5′-untranslated region of the ANKRD26 gene in 9 THC2 families. Here we report on 12 additional pedigrees with ANKRD26 mutations, 6 of which are new. Because THC2 affected 21 of the 210 families in our database, it has to be considered one of the less rare forms of inherited thrombocytopenia. Analysis of all 21 families with ANKRD26 mutations identified to date revealed that thrombocytopenia and bleeding tendency were usually mild. Nearly all patients had no platelet macrocytosis, and this characteristic distinguishes THC2 from most other forms of inherited thrombocytopenia. In the majority of cases, platelets were deficient in glycoprotein Ia and α-granules, whereas in vitro platelet aggregation was normal. Bone marrow examination and serum thrombopoietin levels suggested that thrombocytopenia was derived from dysmegakaryopoiesis. Unexplained high values of hemoglobin and leukocytes were observed in a few cases. An unexpected finding that warrants further investigation was a high incidence of acute leukemia. Given the scarcity of distinctive characteristics, the ANKRD26-related thrombocytopenia has to be taken into consideration in the differential diagnosis of isolated thrombocytopenias.