Fostamatinib effectiveness and safety for immune thrombocytopenia in clinical practice.

Fostamatinib, a recently approved syk inhibitor used in adult primary immune thrombocytopenia (ITP), has been shown to be safe and effective in this disorder. However, clinical trial results may not be similarly reproduced in clinical practice. Here 138 ITP patients (both primary and secondary) from 42 Spanish centers who had been treated with fostamatinib were evaluated prospectively and retrospectively. The median age of our cohort (55.8% women) was 66 years (interquartile range, IQR, 56-80 years). The median time since ITP diagnosis at fostamatinib initiation was 51 months (IQR, 10-166 months). The median number of therapies prior to fostamatinib initiation was 4 (IQR, 2-5), including eltrombopag (76.1%), romiplostim (57.2%) and intravenous immunoglobulins (IVIG) (44.2%). Fifty-eight patients (42.0%) had signs/symptoms of bleeding in the month prior to treatment initiation. 79.0% of patients responded to fostamatinib with 53.6% complete responses (platelet count > 100 x 109 /L). Eighty-three patients (60.1%) received fostamatinib monotherapy achieving a high response rate (85.4%). The proportion of time in response during the 27-month period examined was 83.3%. The median time to platelet response was 11 days (IQR, 7-21 days). Sixty-seven patients (48.5%) experienced adverse events, mainly grade 1-2, the commonest of which were diarrhea (n = 28) and hypertension (n = 21). One patient had deep venous thrombosis and one patient developed acute myocardial infarction. Fostamatinib was shown to be effective with good safety profile in patients with primary and secondary ITP across a wide age spectrum in this real-world study.

A decade of changes in management of immune thrombocytopenia, with special focus on elderly patients.

BACKGROUND: Ten years after their availability, thrombopoietin receptor agonists (TPO-RA) have heralded a paradigm shift in the treatment of immune thrombocytopenia (ITP). This study was aimed to analyze the implementation of current recommendations in the standard practice of adult ITP patients, and how age may influence those changes. METHODS: We included 121 adult patients (> 65 years, n = 54; younger individuals, n = 67) who initiated treatment with TPO-RA between January 2012 and December 2014. RESULTS: Patients older than 65 years treated with TPO-RA presented at diagnosis with significantly higher platelet counts, less bleeding, and a more prothrombotic profile than younger ones. The high efficacy rates of TPO-RA, preferentially used during the last decade in non-chronic phases, precluded from further therapies in the majority of ITP patients. Their administration was associated with a sharp decline in the last decade in the use of splenectomy and intravenous immunoglobulin, especially in younger ITP individuals. CONCLUSION: These results confirm (1) that there is a preferential use of TPO-RAs in elderly ITP patients with fewer bleeding complications but more unfavorable prothrombotic conditions than in younger individuals, and (2) that early use of these agents has been established as an effective therapeutic alternative to other second line therapies.

Elucidating the Mechanism of Action of the Attributed Immunomodulatory Role of Eltrombopag in Primary Immune Thrombocytopenia: An In Silico Approach.

Eltrombopag is a thrombopoietin receptor (MPL) agonist approved for the treatment of primary immune thrombocytopenia (ITP). Recent evidence shows that some patients may sustain platelet counts following eltrombopag discontinuation. The systemic immunomodulatory response that resolves ITP in some patients could result from an increase in platelet mass, caused either by the direct action of eltrombopag on megakaryocytes through MPL stimulation, or potential MPL-independent actions on other cell types. To uncover the possible mechanisms of action of eltrombopag, in silico analyses were performed, including a systems biology-based approach, a therapeutic performance mapping system, and structural analyses. Through manual curation of the available bibliography, 56 key proteins were identified and integrated into the ITP interactome analysis. Mathematical models (94.92% mean accuracy) were obtained to elucidate potential MPL-dependent pathways in non-megakaryocytic cell subtypes. In addition to the effects on megakaryocytes and platelet numbers, the results were consistent with MPL-mediated effects on other cells, which could involve interferon-gamma, transforming growth factor-beta, peroxisome proliferator-activated receptor-gamma, and forkhead box protein P3 pathways. Structural analyses indicated that effects on three apoptosis-related proteins (BCL2L1, BCL2, BAX) from the Bcl-2 family may be off-target effects of eltrombopag. In conclusion, this study proposes new hypotheses regarding the immunomodulatory functions of eltrombopag in patients with ITP.

Platelet activation and neutrophil extracellular trap (NET) formation in immune thrombocytopenia: is there an association?

No biological predictors for the increased risk of thrombosis in patients with immune thrombocytopenia (ITP) have been identified. The aim of the study was to investigate platelet and neutrophil activation as well neutrophil extracellular trap (NET) formation in 63 ITP patients and 30 healthy volunteers. Platelet and neutrophil activation was assessed during steady state using flow cytometry analysis, and NETs were evaluated by quantitation of cell free DNA (cfDNA), and citrullinated histone-3-DNA (CitH3-DNA). Patient platelets and neutrophils showed increased CD62 and CD11b expression compared to controls (p = .038, and p = .022, respectively). In patients, platelet activation inversely correlated with platelet count and platelet size (p < .001), and positively correlated with neutrophil degranulation (p = .024). More NET formation, both CitH3-DNA (p = .025) and cfDNA(p < .001), were present in ITP patients compared to controls. CitH3-DNA inversely correlated with CD62 expression on platelets (p = .042), but higher levels of cfDNA were observed in individuals with classical cardiovascular risk factors for thrombosis, and in those with a previous history of thrombotic events. In this disease, the increased platelet activation and plasma NET levels seem to be separable processes that associate (either positively or inversely in the case of CitH3-DNA or platelet degranulation, respectively) to platelet mass.

MicroRNAs as potential regulators of platelet function and bleeding diatheses.

Although a growing number of studies suggest that microRNAs (miRNAs) play a relevant role in platelet biology, their implications in bleeding diatheses are starting to be investigated. Indeed, several studies have shown that alterations in the intracellular levels of highly expressed platelet miRNAs provoke a thrombotic phenotype. On the other hand, primary immune thrombocytopenia (ITP), which is considered the hallmark of acquired bleeding disorders, has been recently associated with altered levels of miRNAs in peripheral blood mononuclear cells, plasma, and platelets. In this review, we will focus on miRNAs that may affect the hemostatic and thrombotic functions of platelets, and we will discuss the different studies that have attempted to associate miRNAs with regulatory mechanisms of ITP.

Introducing high-throughput sequencing into mainstream genetic diagnosis practice in inherited platelet disorders.

Inherited platelet disorders are a heterogeneous group of rare diseases, caused by inherited defects in platelet production and/or function. Their genetic diagnosis would benefit clinical care, prognosis and preventative treatments. Until recently, this diagnosis has usually been performed via Sanger sequencing of a limited number of candidate genes. High-throughput sequencing is revolutionizing the genetic diagnosis of diseases, including bleeding disorders. We have designed a novel high-throughput sequencing platform to investigate the unknown molecular pathology in a cohort of 82 patients with inherited platelet disorders. Thirty-four (41.5%) patients presented with a phenotype strongly indicative of a particular type of platelet disorder. The other patients had clinical bleeding indicative of platelet dysfunction, but with no identifiable features. The high-throughput sequencing test enabled a molecular diagnosis in 70% of these patients. This sensitivity increased to 90% among patients suspected of having a defined platelet disorder. We found 57 different candidate variants in 28 genes, of which 70% had not previously been described. Following consensus guidelines, we qualified 68.4% and 26.3% of the candidate variants as being pathogenic and likely pathogenic, respectively. In addition to establishing definitive diagnoses of well-known inherited platelet disorders, high-throughput sequencing also identified rarer disorders such as sitosterolemia, filamin and actinin deficiencies, and G protein-coupled receptor defects. This included disease-causing variants in DIAPH1 (n=2) and RASGRP2 (n=3). Our study reinforces the feasibility of introducing high-throughput sequencing technology into the mainstream laboratory for the genetic diagnostic practice in inherited platelet disorders.

Mesothelial-to-mesenchymal transition in the pathogenesis of post-surgical peritoneal adhesions.

Peritoneal adhesions (PAs) are fibrotic bands formed between bowel loops, solid organs, and the parietal peritoneum, which may appear following surgery, infection or endometriosis. They represent an important health problem with no effective treatment. Mesothelial cells (MCs) line the peritoneal cavity and undergo a mesothelial-to-mesenchymal transition (MMT) under pathological conditions, transforming into myofibroblasts, which are abundant in peritoneal fibrotic tissue. The aim of this study was to investigate if peritoneal MCs undergo a MMT contributing to the formation of post-surgical adhesions. Biopsies from patients with PAs were analysed by immunohistochemistry, immunofluorescence, and quantitative RT-PCR. A mouse model of PAs based on ischaemic buttons was used to modulate MMT by blocking the transforming growth factor-beta (TGF-ß) pathway. The severity of adhesions and MMT-related marker expression were studied. We observed myofibroblasts derived from the conversion of MCs in submesothelial areas of patients with PAs. In addition, MMT-related markers were dysregulated in adhesion zones when compared to distant normal peritoneal tissue of the same patient. In animal experiments, blockage of TGF-ß resulted in molecular reprogramming of markers related to the mesenchymal conversion of MCs and in a significant decrease in the severity of the adhesions. These data indicate for the first time that MMT is involved in PA pathogenesis. This finding opens new therapeutic strategies to interfere with adhesion formation by modulating MMT with a wide range of pharmacological agents.

Persistent cytotoxic T lymphocyte expansions after allogeneic haematopoietic stem cell transplantation: kinetics, clinical impact and absence of STAT3 mutations.

Peripheral expansion of cytotoxic T lymphocytes (CTL) derived from the graft in the initial stages of allogeneic haematopoietic stem cell transplantation (alloHSCT) immune recovery is a well-known physiological event. The description of symptomatic large granular lymphocyte leukaemia in this setting may generate uncertainty, mostly in those cases in which the CTL expansion (CTLe) persists beyond the early transplantation period. We aimed to assess the nature of CTLe during the post-alloHSCT period in 154 adult patients with a long-term surveillance. We studied the longitudinal kinetics of those expansions, their relationship to clinical events, and their phenotypic and molecular features, including recently reported CTL leukaemia-STAT3 mutations. Persistent relative CTLe cases are frequent (49%), related with thymoglobulin prophylaxis (P ≤ 0·001), acute graft-versus-host disease (GVHD, P = 0·02), and reduced intensity conditioning (P = 0·04). Absolute CTLe are scarce (9%) and related to chronic GVHD. T cell receptor rearrangement was reported as clonal and oligoclonal in the majority of patients with CTLe. The absence of STAT3 mutations and the CD8/CD4 declining longitudinal kinetics in the late period supports its benign nature, expressed clinically by the null detrimental impact of these expansions on post-transplant outcome and/or serious infectious events.

Chediak-Higashi syndrome: description of two novel homozygous missense mutations causing divergent clinical phenotype.

Chediak-Higashi syndrome (CHS) is a rare autosomal recessive disease resulting from mutations in the LYST/CHS1 gene, which encodes for a 429 kDa protein, CHS1/LYST, that regulates vesicle trafficking and determines the size of lysosomes and other organelles. To date, 60 different mutations have been characterized, and a reasonably straightforward phenotype-genotype correlation has been suggested. We describe two patients on opposite ends of the CHS clinical spectrum with novel missense mutations. We characterized these patients in terms of their mutations, protein localization and expression, mRNA stability, and electrostatic potential. Patient 1 is the first report of a severe early-onset CHS with a homozygous missense mutation (c.11362 G>A, p.G3725R) in the LYST/CHS1 gene. This molecular change results in a reduction at the CHS1 protein level, not due to an mRNA effect, but maybe a consequence of both, a change in the structure of the protein and most likely attributable to the remarkable serious perturbation in the electrostatic potential. Patient 2, who exhibited the adolescence form of the disease, was found to be homozygous for a novel missense mutation c.961 T>C, p.C258R, which seemed to have minor effect on the structure of the CHS1/LYST protein. Reexamining accepted premises of missense mutant alleles being reported among patients with clinically mild forms of the disorder should be carried out, and attempts to link genotype and clinical phenotype require identifying the actual molecular effect of the mutation. Early and accurate diagnosis of the severity of the disease is extremely important to early differentiate patients who would benefit from premature enrollment into a transplantation protocol.

Epidemiology, Treatment Patterns, and Cost Analysis of Immune Thrombocytopenia in Spain between 2014 and 2020: A Population-based Study.

Background Immune thrombocytopenia (ITP) is characterised by low platelet counts and often leads to bleeding, fatigue, and reduced health-related quality of life. Methods This observational, retrospective, population-based study using BIG-PAC® database included Spanish paediatric and adult patients with primary ITP diagnosed in primary care and hospitals between 2014 and 2020 (median follow-up: 4 years). Epidemiology, baseline/clinical characteristics, treatment trends, healthcare resources and costs were analysed. Results The BIG-PAC® database contains records of 1,818,588 patients; 170 adults and 27 children with ITP were included in our analysis. ITP prevalence and annual incidence per 100,000 were estimated in 10.8 (2.8 in chronic ITP [cITP] patients) and 1.5 (0.3 in cITP patients), respectively. Epistaxis was the most common bleeding event, followed by genitourinary and gastrointestinal bleeding; >50%/> 75% of ITP/cITP patients reported fatigue. Chronic patients had lower platelet counts at baseline and required more transfusions. Corticosteroids, immunosuppressants, and thrombopoietin receptor agonists were the most used agents in first-, second- and third-line treatment, respectively. Thirty-five patients, all of them in chronic phase, underwent splenectomy. Patients had on average 13.9, 6.6, and 1.2 visits/year to primary care, haematology/internal medicine, and emergency departments, respectively. More than one-fourth of adult patients took on average 16.3 days of sick leave annually. Mean annual total health care costs were €10,741 (ITP patients) and €19,809 (cITP patients). Conclusion This is the first study to provide an overall perspective on the situation of the Spanish ITP population in terms of epidemiology, treatment trends, health care resources and costs, highlighting unmet patient needs, and direct and indirect costs/resource use between 2014 and 2020.

Targeted long-read sequencing identifies and characterizes structural variants in cases of inherited platelet disorders.

BACKGROUND: Genetic diagnosis of inherited platelet disorders (IPDs) is mainly performed by high-throughput sequencing (HTS). These short-read-based sequencing methods sometimes fail to characterize the genetics of the disease. OBJECTIVES: To evaluate nanopore long-read DNA sequencing for characterization of structural variants (SVs) in patients with IPDs. METHODS: Four patients with a clinical and laboratory diagnosis of Glanzmann thrombasthenia (GT) (P1 and P2) and Hermansky-Pudlak syndrome (HPS) (P3 and P4) in whom HTS missed the underlying molecular cause were included. DNA was analyzed by both standard HTS and nanopore sequencing on a MinION device (Oxford Nanopore Technologies) after enrichment of DNA spanning regions covering GT and HPS genes. RESULTS: In patients with GT, HTS identified only 1 heterozygous ITGB3 splice variant c.2301+1G>C in P2. In patients with HPS, a homozygous deletion in HPS5 was suspected in P3, and 2 heterozygous HPS3 variants, c.2464C>T (p.Arg822∗) and a deletion affecting 2 exons, were reported in P4. Nanopore sequencing revealed a complex SV affecting exons 2 to 6 in ITGB3 (deletion-inversion-duplication) in homozygosity in P1 and compound heterozygosity with the splice variant in P2. In the 2 patients with HPS, nanopore defined the length of the SVs, which were characterized at nucleotide resolution. This allowed the identification of repetitive Alu elements at the breakpoints and the design of specific polymerase chain reactions for family screening. CONCLUSION: The nanopore technology overcomes the limitations of standard short-read sequencing techniques in SV characterization. Using nanopore, we characterized novel defects in ITGB3, HPS5, and HPS3, highlighting the utility of long-read sequencing as an additional diagnostic tool in IPDs.

Thrombotic risk and features of patients with inferior vena cava agenesis: a multicentre, retrospective, observational study.

BACKGROUND: Inferior vena cava agenesis (IVCA) is a rare anomaly predisposing affected people to lower-limb venous thrombosis with low frequency of pulmonary embolism. Antenatal thrombosis and inherited thrombophilia have been suggested as causes of IVCA. However, there is little evidence on the clinical course and management of this condition. We designed a patient registry to assess the thrombotic risk and features of IVCA. METHODS: In this this multicentre, retrospective, observational study, we included patients with IVCA diagnosed by routine imaging from 20 hospitals in Spain (n=18), Portugal (n=1), and Italy (n=1). Patients were identified from a systematic search in radiology databases using data extraction software (cohort A) and alternative searches in medical records for confirmed IVCA (cohort B; option allowed when systematic approaches were unapplicable). Primary outcomes were clinical and imaging features, thrombotic risk, phenotype of IVCA-associated thrombosis, anticoagulant treatment, and the results of thrombophilia testing. FINDINGS: We included patients with IVCA diagnosed by routine imaging studies done between Jan 1, 2010, and Dec 31, 2022. In the systematic search, 4 341 333 imaging exams were screened from the radiology databases of eight centres. 122 eligible patients were enrolled in cohort A. A further 95 patients were identified by screening medical records at 12 centres, of whom 88 were eligible and included in cohort B, making a combined cohort of 210 patients. 96 (46%) of 210 patients were female and 200 (95%) were European or Hispanic. 60 (29%) of 210 patients had hepatic IVC interruption, whereas 150 (71%) had extrahepatic IVCA. In cohort A, 65 (53%) of 122 patients had venous thrombosis, with an estimated annual risk of 1·15% (95% CI 0·89-1·46). Extrahepatic IVCA was associated with a greater risk of venous thrombosis than hepatic IVCA (56 [67%] of 84 patients vs nine [24%] of 38 patients, odds ratio 5·31, 95% CI 2·27-12·43; p<0·0001). Analysis of 126 patients with venous thrombosis pooled from cohorts A and B showed early-onset (median age 34·6 years, IQR 23·3-54·3) and recurrent events (50 [40%] of 126 patients). Patients with extrahepatic IVCA had greater proportions of lower-limb venous thrombosis (95 [87%] of 109 vs nine [53%] of 17, p=0·0010) and recurrence (48 [44%] of 109 vs two [12%] of 17, p=0·015), but lower rates of pulmonary embolism (10 [10%] of 99 vs four [33%] of 12, p=0·044) than did patients with hepatic IVCA. 77 (63%) of 122 patients with thrombosis underwent indefinite anticoagulation. 32 (29%) of 111 patients (29 [34%] of 86 with thrombosis) had coexisting thrombophilias. The recurrence risk was lower for patients receiving indefinite anticoagulation (adjusted odds ratio 0·24, 95% CI 0·08-0·61; p=0·010), and greater for thrombophilias (3·19, 1·09-9·32; p=0·034). INTERPRETATION: This evaluation of a large patient cohort demonstrates the high thrombotic burden of IVCA. We have identified two distinct forms of IVCA, hepatic and extrahepatic, suggesting different underlying mechanisms. Beyond clinical characterisation, we draw attention to this orphan disease and highlight the need for its study and improved care. FUNDING: Spanish Society of Thrombosis and Haemostasis, Instituto de Salud Carlos III, FEDER, Fundación Séneca.

Inflammatory microRNAs in cardiovascular pathology: another brick in the wall.

The regulatory role of microRNAs (miRNAs) is mainly mediated by their effect on protein expression and is recognized in a multitude of pathophysiological processes. In recent decades, accumulating evidence has interest in these factors as modulatory elements of cardiovascular pathophysiology. Furthermore, additional biological processes have been identified as new components of cardiovascular disease etiology. In particular, inflammation is now considered an important cardiovascular risk factor. Thus, in the present review, we will focus on the role of a subset of miRNAs called inflamma-miRs that may regulate inflammatory status in the development of cardiovascular pathology. According to published data, the most representative candidates that play functional roles in thromboinflammation are miR-21, miR-33, miR-34a, miR-146a, miR-155, and miR-223. We will describe the functions of these miRNAs in several cardiovascular pathologies in depth, with specific emphasis on the molecular mechanisms related to atherogenesis. We will also discuss the latest findings on the role of miRNAs as regulators of neutrophil extracellular traps and their impact on cardiovascular diseases. Overall, the data suggest that the use of miRNAs as therapeutic tools or biomarkers may improve the diagnosis or prognosis of adverse cardiovascular events in inflammatory diseases. Thus, targeting or increasing the levels of adequate inflamma-miRs at different stages of disease could help mitigate or avoid the development of cardiovascular morbidities.

microRNAs as biomarkers of risk of major adverse cardiovascular events in atrial fibrillation.

Atrial fibrillation is a complex and multifactorial disease. Although prophylactic anticoagulation has great benefits in avoiding comorbidities, adverse cardiovascular events still occur and thus in recent decades, many resources have been invested in the identification of useful markers in the prevention of the risk of MACE in these patients. As such, microRNAs, that are small non-coding RNAs whose function is to regulate gene expression post-transcriptionally, have a relevant role in the development of MACE. miRNAs, have been investigated for many years as potential non-invasive biomarkers of several diseases. Different studies have shown their utility in the diagnosis and prognosis of cardiovascular diseases. In particular, some studies have associated the presence of certain miRNAs in plasma with the development of MACE in AF. Despite these results, there are still many efforts to be done to allow the clinical use of miRNAs. The lack of standardization concerning the methodology in purifying and detecting miRNAs, still provides contradictory results. miRNAs also have a functional impact in MACE in AF through the dysregulation of immunothrombosis. Indeed, miRNAs may be a link between MACE and inflammation, through the regulation of neutrophil extracellular traps that are a key element in the establishment and evolution of thrombotic events. The use of miRNAs as therapy against thromboinflammatory processes should also be a future approach to avoid the occurrence of MACE in atrial fibrillation.

Lentiviral gene therapy reverts GPIX expression and phenotype in Bernard-Soulier syndrome type C.

Bernard-Soulier syndrome (BSS) is a rare congenital disease characterized by macrothrombocytopenia and frequent bleeding. It is caused by pathogenic variants in three genes (GP1BA, GP1BB, or GP9) that encode for the GPIbα, GPIbß, and GPIX subunits of the GPIb-V-IX complex, the main platelet surface receptor for von Willebrand factor, being essential for platelet adhesion and aggregation. According to the affected gene, we distinguish BSS type A1 (GP1BA), type B (GP1BB), or type C (GP9). Pathogenic variants in these genes cause absent, incomplete, or dysfunctional GPIb-V-IX receptor and, consequently, a hemorrhagic phenotype. Using gene-editing tools, we generated knockout (KO) human cellular models that helped us to better understand GPIb-V-IX complex assembly. Furthermore, we developed novel lentiviral vectors capable of correcting GPIX expression, localization, and functionality in human GP9-KO megakaryoblastic cell lines. Generated GP9-KO induced pluripotent stem cells produced platelets that recapitulated the BSS phenotype: absence of GPIX on the membrane surface and large size. Importantly, gene therapy tools reverted both characteristics. Finally, hematopoietic stem cells from two unrelated BSS type C patients were transduced with the gene therapy vectors and differentiated to produce GPIX-expressing megakaryocytes and platelets with a reduced size. These results demonstrate the potential of lentiviral-based gene therapy to rescue BSS type C.

NLRP3 inflammasome activation and symptom burden in KRAS-mutated CMML patients is reverted by IL-1 blocking therapy.

Chronic myelomonocytic leukemia (CMML) is frequently associated with mutations in the rat sarcoma gene (RAS), leading to worse prognosis. RAS mutations result in active RAS-GTP proteins, favoring myeloid cell proliferation and survival and inducing the NLRP3 inflammasome together with the apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), which promote caspase-1 activation and interleukin (IL)-1ß release. Here, we report, in a cohort of CMML patients with mutations in KRAS, a constitutive activation of the NLRP3 inflammasome in monocytes, evidenced by ASC oligomerization and IL-1ß release, as well as a specific inflammatory cytokine signature. Treatment of a CMML patient with a KRASG12D mutation using the IL-1 receptor blocker anakinra inhibits NLRP3 inflammasome activation, reduces monocyte count, and improves the patient's clinical status, enabling a stem cell transplant. This reveals a basal inflammasome activation in RAS-mutated CMML patients and suggests potential therapeutic applications of NLRP3 and IL-1 blockers.

New developments in the diagnosis of primary immune thrombocytopenia.

Immune thrombocytopenia is an acquired autoimmune disorder, which can affect both adults and children, characterized by lower than normal platelet counts (below 100 × 109/l). Thrombocytopenia may result in an increased risk of bleeding and puts patients at risk for serious complications. In the last decade, the multifactorial pathogenesis of ITP has become apparent, leading to greater understanding that different immune-mediated mechanisms could be involved in each patient, explaining the variable clinical presentation and response to therapies. The management of ITP patients has changed considerably in these past 10 years, but diagnosis of the disease has changed little, and remains clinical and possible only with the exclusion of other causes of thrombocytopenia. Although the search for such a test continues, to date, there is no reliable biomarker or gold-standard diagnostic test, which contributes to the high rate of misdiagnosis of the disease. This review presents the current limitations in the identification of the molecular disease underlying this disorder.