Bernard-Soulier syndrome caused by two novel heterozygous GP1BA gene mutations: a case report and literature review.

BACKGROUND: Bernard-Soulier syndrome (BSS) is a rare inherited macrothrombocytopenia, usually autosomal recessive, which is characterized by prolonged bleeding, thrombocytopenia, and abnormally large platelets. METHODS: For more than 6 years, we misdiagnosed a patient with BSS without an obvious bleeding tendency as having idiopathic thrombocytopenia purpura (ITP), prior to obtaining a genetic analysis. On admission, routine hematology showed a platelet count of 30 × 109/L and mean platelet volume (MPV) of 14.0 fL. RESULTS: Whole-exome sequencing revealed two likely pathogenic heterozygous mutations (c.95_101del and c.1012del) in GP1BA. Flow cytometry analysis of platelet membrane glycoproteins indicated that the expression of GP1b was 0.28% of the normal level. Platelet aggregation tests indicated that platelet aggregation was inhibited by ristocetin- (1.7%), ADP- (14.5%), and arachidonic acid- (5.6%) induced platelet aggregation. A literature review identified reports on 53 mutations in the GP1BA gene in 253 patients, 29 mutations in the GP1BB gene in 90 patients, and 32 mutations in the GP9 gene in 114 patients. CONCLUSION: This case report describes two novel gene mutation sites that have not been reported previously, enriching understanding of the GP1BA mutation spectrum.

Point-of-care platelet function testing results in a dog with Bernard-Soulier syndrome.

Bernard-Soulier syndrome (BSS), also known as hemorrhagiparous thrombocytic dystrophy (OMIA 002207-9615), is a rare defect in platelet function recognized in both dogs and humans. It is caused by a deficiency in glycoprotein 1b-IX-V, the platelet surface protein which acts as a receptor for the von Willebrand factor. The characteristic features of BSS in humans and dogs include macrothrombocytes and mild-to-moderate thrombocytopenia with a bleeding tendency. This condition has previously been reported in European Cocker Spaniel dogs; however, the results of platelet function tests in these animals have not been reported. This case report describes a European Cocker Spaniel dog with spontaneously occurring Bernard-Soulier syndrome and the results of point-of-care platelet function tests, including a prolonged buccal mucosal bleeding time (>8 min), prolongation (>300 s) of PFA-200 COL/ADP, COL/EPI, and P2Y closure times, and reduced aggregation (15%-48%) with Plateletworks ADP, but with normal aggregation (92%) with Plateletworks AA. This is the first description of the results of platelet function tests in canine Bernard-Soulier syndrome.

Clinical Dilemma, Bernard Soulier Syndrome versus Immune Thrombocytopenic Purpura: A Case Report.

BACKGROUND: Bernard Soulier Syndrome (BSS) is a rare autosomal recessive disorder due to deficiency or dysfunction of the glycoprotein GPIb-V-IX complex on the platelet surface. It is also known as hemorrhagiparous thrombocytic dystrophy or congenital hemorrhagiparous thrombocytic dystrophy. The patient usually presents with severe and prolonged bleeding along with characteristics of giant blood platelets and low platelet counts. Manifestations of BSS include epistaxis, gum bleeding, purpuric rashes, menorrhagia, rarely melena, and hematemesis. On the other hand, immune thrombocytopenic purpura (ITP) is an acquired autoimmune disorder in which there is accelerated platelet destruction and reduced platelet production. Isolated thrombocytopenia without fever, lymphadenopathy, and organomegaly usually lead to the diagnosis of immune thrombocytopenia. CASE PRESENTATION: A 20 years old female presented with complaints of recurrent episodes of epistaxis since childhood and menorrhagia during menarche. She was misdiagnosed as ITP elsewhere. Later, based on thorough clinical examination and investigation, the diagnosis was confirmed as BSS. CONCLUSION: BSS should always be taken in the differential diagnosis of ITP, especially when persistent, refractory, and treated unsuccessfully with steroids or splenectomy.

Bernard-Soulier Syndrome from the Perspective of the Obstetrician: A Case Report with a Review of the Literature.

OBJECTIVE: Bernard-Soulier syndrome (BSS) is one of the rare inherited platelet disorders that is characterized by macrothrombocytopenia and adhesion abnormality due to the absence or malfunctioning of the membrane GPIb-IX-V complex. There is no high-quality evidence on obstetric management of BSS owing to its rarity. Here we report an uncomplicated delivery of an adolescent with BSS and review the literature on the topic of BSS and pregnancy. METHODS: PUBMED, EMBASE, COCHRANE, and Google Scholar databases were searched up to April 2022 without language and year restriction using the terms "Bernard Soulier" and "Pregnancy". The primary objectives were to evaluate maternal and fetal outcomes. The secondary objectives were to analyze pregnancy complications, gestational age at delivery, mode of delivery, administered prophylaxis, treatment approaches, duration of postpartum hospitalization, and the postpartum requirement of blood and blood product. RESULTS: The patient was a 19-year-old and 39-week pregnant woman who was diagnosed with BSS at the age of 10 by flow cytometry and genetic analysis. Single donor platelet transfusions and oral tranexamic acid were administered as prophylaxis at the peripartum period. She was delivered by cesarean section due to failure of labor. The postpartum period was uneventful for both mother and neonate. In the literature review, postpartum hemorrhage (PPH) was found in 52.9% (27/51) of deliveries. Late PPH occurred more frequently than early PPH (35.3 and 31.4%, respectively). 49% (25/51) of pregnancies had severe thrombocytopenia, and antepartum hemorrhage was observed in 11.8% (6/51) of those. The platelet count was in close relation to antenatal complications. 64.7% (33/51) of the patients were delivered via cesarean section. PPH and late PPH were found to be more common in those who delivered vaginally compared to those who delivered by caesarean section. It was observed that PPH was less common in women who were given prophylaxis in the peripartum period. CONCLUSION: BSS is an inherited macro-thrombocytopathy that may cause adverse maternal and neonatal outcomes. The optimal mode and timing of delivery remain unclear. A multidisciplinary approach with prophylaxis at the peripartum period should be applied.

Opening Pandora's box: abnormal genetic carrier screening and need for lifetime follow-up.

OBJECTIVE: Expanded carrier screening (ECS) is rising in popularity because of its application in a diverse population, its decreasing cost, and efficiency.1 However, it has traditionally been used to assess fetal risk. The next generation sequencing ECS panel offered at our academic medical center consists of 283 genes associated with hereditary disorders. Of those, 20 (7.1%) are autosomal recessive conditions, notable for variable expression of the clinical phenotype in heterozygous carriers, which may increase maternal risk for malignancy, bleeding, cardiovascular, or rheumatologic disease. Another 21 (7.4%) are X-linked conditions. We aimed to evaluate the prevalence of variants that have a potential for maternal phenotypic expression and whether identification of specific variants prompted patients to pursue further care in our health system, namely comprehensive genetic counseling and further healthcare consults when recommended. STUDY DESIGN: An institutional review board-approved descriptive retrospective cohort study was performed in a New York City academic medical center at which reproductive aged women were offered universal ECS from 2018 to 2021 by their provider, inclusive of obstetrician-gynecologists, maternal-fetal medicine physicians, and genetic counselors. Pretest counseling was performed by the ordering provider. Patients found to carry mutations with the potential for maternal phenotypic expression were contacted by genetic counselors regarding their clinical risks. In addition, patients who were carriers for factor XI deficiency, Bernard Soulier syndrome, ataxia telangectesia, fumarase deficiency, Nijmegen breakage syndrome, Duchenne muscular dystrophy, and familial hypercholesterolemia were advised to seek specialized healthcare pertaining to their clinical risk. The genetic counseling summary was placed in the electronic medical records (EMRs) so that the primary provider could view the findings. Through our EMRs, we evaluated the rates of healthcare uptake among these patients for at least 1 year after delivery. RESULTS: In total, 168 of 1184 (14.2%) patients were identified as carriers of mutations with a potential for maternal phenotypic expression. Of these, 156 (93%) were pregnant and 12 (7%) were preconception. Of those patients, 143 (85%) were carriers of autosomal recessive traits (Figure 1), whereas 22 of 168 (13%) patients were carriers of X-linked conditions (Figure 2) and 3 of 168 (2%) patients carried both autosomal recessive traits and X-linked conditions. Of these carriers, 132 of 168 (78.6%) patients underwent genetic counseling. The most common heterozygous mutations were sickle cell trait (25.6%), thalassemia (alpha and/or beta) trait (14.2%), factor XI deficiency (4.7%), dystrophic epidermolysis bullosa (4.2%), and Alport syndrome (4.1%). Two patients were diagnosed as homozygous carriers of nonclassical congenital adrenal hyperplasia. During the study period, 23 of 168 (13.6%) patients were heterozygous for specific pathogenic variants (inclusive of factor XI, Bernard Soulier syndrome, ataxia telangectesia, fumarase deficiency, Nijmegen breakage syndrome, Duchenne muscular dystrophy, and familial hypercholesterolemia) and were advised to seek specialized healthcare pertaining to these findings. Of these, 20 (87.0%) received genetic counseling with standardized recommendations, however, only 4 of 23 (17%) patients pursued the recommended referrals during our study period. CONCLUSION: This study described the follow-up rates among patients identified as carriers of conditions with the potential for maternal phenotypic expression using ECS. We observed that 14.2% of patients who underwent ECS were identified as carriers of genetic mutations with the potential for maternal phenotypic expression, and of the 23 who were recommended specific care because a pathogenic variant was identified, only 17.4% of patients followed the recommendations. We believe that as ECS implementation becomes widespread, more maternal carriers with clinical risk to themselves will be identified. Therefore, as we open this Pandora's box, the burden of counseling and follow-up must be addressed.

Biological, clinical features and modelling of heterozygous variants of glycoprotein Ib platelet subunit alpha (GP1BA) and glycoprotein Ib platelet subunit beta (GP1BB) genes responsible for constitutional thrombocytopenia.

Constitutional thrombocytopenias are rare disorders, often difficult to discriminate from acquired thrombocytopenias. More than 80 genes have been described as being at the origin of these diseases. Among them, several variants of the glycoprotein Ib platelet subunit alpha (GP1BA) and glycoprotein Ib platelet subunit beta (GP1BB) genes, coding for the GpIb-IX-V glycoprotein complex, have been reported in the literature. The study reported here aimed at describing newly identified monoallelic anomalies affecting the GP1BA and GP1BB genes on a clinical, biological and molecular level. In a cohort of nine patients with macrothrombocytopenia, eight heterozygous variants of the GP1BA or GP1BB genes were identified. Five of them had never been described in the heterozygous state. Computer modelling disclosed structure/function relationships of these five variants.

Bernard-Soulier syndrome in pregnancy with retinal detachment: a rare phenomenon.

Bernard-Soulier syndrome (BSS) is a rare congenital bleeding disorder of the platelet, and it is mainly inherited as an autosomal recessive trait. It is caused by both qualitative and quantitative deficiency of the platelet membrane glycoprotein (GP) Ib-IX-V receptor complex, thereby causing abnormal platelets adhesion.We report a case of a primigravida in her 20s with history of BSS diagnosed in childhood due to family history. Her preconception period was challenging as she suffered from severe menorrhagia often requiring hospital admission, blood and platelet transfusions.At 35 weeks gestation, she developed temporal crowded retinal detachment of the left eye and had a successful left scleral buckling surgery under general anaesthesia (GA).She had a multidisciplinary team care with a successful elective GA caesarean section at 39+3 weeks gestation with peridelivery platelet transfusion and intravenous recombinant factor VIIa. Regional anaesthesia, intramuscular injections and anticoagulation were avoided.

Characterization of zebrafish gp1ba mutant and modelling Bernard Soulier syndrome.

The aim of this study is to model classical Bernard Soulier Syndrome in the zebrafish by targeting Gp1ba. We obtained gp1ba mutant embryos from Zebrafish International Resource Center and grew them to adulthood. The tail clips from these fish were used to prepare DNA and sequenced to identify heterozygotes. They were then bred to obtain homozygotes. The mutation was confirmed by DNA sequencing as a termination codon UAA in place of AAA codon at position 886 in the gp1ba transcript. Thus, at the Pro-295, the Gp1ba protein could be terminated. The blood from gp1ba homozygous and heterozygous mutants showed decreased ristocetin-mediated agglutination in the whole blood agglutination assay. The gp1ba heterozygous and homozygous larvae were subjected to a laser-assisted arterial thrombosis assay, and the results showed the prolonged occlusion in the caudal artery. These results suggested that the gp1ba mutant had a bleeding phenotype. The blood smears from the adult gp1ba, heterozygous and homozygous mutants, showed macrothrombocytes, similar to the human GP1BA deficiency that showed giant platelets. The bleeding assay on these heterozygous and homozygous mutants showed greater bleeding than wildtype, confirming the above findings. Taken together, the characterization of gp1ba zebrafish mutant suggested an autosomal dominant mode of inheritance. The zebrafish gp1ba mutant models classical Bernard Soulier Syndrome and could be used for reversing this phenotype to identify novel factors by the genome-wide piggyback knockdown method.

Iron deficiency anemia and bleeding management in pediatric patients with Bernard-Soulier syndrome and Glanzmann Thrombasthenia: A single-institution analysis.

INTRODUCTION: Frequent and severe bleeding events (SBE) in patients with inherited qualitative platelet disorders Bernard-Soulier Syndrome (BSS) and Glanzmann Thrombasthenia (GT) can lead to secondary iron deficiency anemia (IDA). SBE are primarily treated with platelet transfusions or recombinant activated factor VII (rFVIIa) infusions. The impact of IDA on bleeding management and disease outcomes is understudied. AIM: To evaluate bleeding management, outcomes, and any association with IDA in pediatric patients with BSS and GT. METHODS: Retrospective chart-review of pediatric patients with BSS or GT followed at a single hemophilia treatment center between 2007 and 2019. RESULTS: We identified 14 patients with BSS (n = 2) or GT (n = 12). Patients received rFVIIa (7%), platelet transfusions (7%), or a combination of both (57%) for SBE. Eleven patients (79%) had IDA requiring oral and/or intravenous iron replacement and 50% required red blood cell transfusions. Due to recurrent SBE and refractory IDA, three patients (21%) received rFVIIa prophylaxis at 90 µg/kilogram 2-3 times/week for ≥15 months. Patients initiated on rFVIIa prophylaxis had a median baseline hemoglobin of 9.8 g/dL (min-max: 8.0-10.7 g/dL) compared to 11.7 g/dL (8.4-13.8 g/dL) for patients treated on-demand. Following initiation of rFVIIa prophylaxis, median hemoglobin and ferritin increased by 1.3 g/dL (0.7-2.5 g/dL) and 14.6 ng/mL (0.2-42.9 ng/mL), respectively, and bleeding rates were reduced by 7-78%. CONCLUSION: IDA is a known complication of recurrent bleeding events in individuals with inherited bleeding disorders. Routine monitoring for IDA may help improve bleeding management and reduce bleed burden in BSS/GT.

Murine models of glycoprotein Ib-IX.

The utility of mouse models to dissect the molecular basis of hemostasis and thrombosis is now well established. The anucleate properties of circulating blood platelet and their specialized release from mature megakaryocytes makes the use of in vivo models all the more informative and powerful. Indeed, they are powerful but there do exist limitations. Here, we review the contributions of mouse models to the pathogenesis of the Bernard-Soulier syndrome, their use in platelet-specific gene expression, the recent development of mice expressing both human GPIb-IX and human von Willebrand factor (VWF), and finally the use of GPIb-IX mouse models to examine the impact of platelet biology beyond clotting. The humanization of the receptor and ligand axis is likely to be a major advancement in the characterization of therapeutics in the complex pathogenesis that drives thrombosis. When appropriate, we highlight some limitations of each mouse model, but this is not to minimize the contributions these models to the field. Rather, the limitations are meant to provide context for any direct application to the important mechanisms supporting human primary hemostasis and thrombosis.

Elevated CD9 expression as a potential biomarker for diagnosis of Bernard-Soulier syndrome.

Diagnosis of inherited platelet glycoprotein disorders is based on specific laboratory techniques such as aggregometry and flow cytometry. Flowcytometry is a powerful method, but equivocal results are produced in some cases. New cluster of differentiation markers could resolve the diagnostic dilemmas. Abnormal expression of CD9 in Bernard-Soulier syndrome (BSS) is recently reported. We aimed to determine the diagnostic significance of CD9 expression in a cohort of Iranian patients with inherited platelet glycoprotein defects. Twelve BSS, 21 Glanzmann thrombasthenia and 16 healthy controls were included in the present study. Flowcytometric diagnosis of BSS and Glanzmann thrombasthenia was made by analysis of CD41/61 and CD42a/42b CD markers. Moreover, phycoerythrin-labelled anti CD9 was examined in patients and healthy controls. The mean fluorescence intensity (MFI) of CD9 among the three groups was compared using suitable statistical methods and a P value of less than 0.05 considered statistically significant. Mean MFI of CD9 was 990.0 in BSS patients versus 421.2 and 317.3 in individuals with Glanzmann thrombasthenia and healthy controls, respectively (P < 0.05). Between the two-group comparison of means by the Mann-Whitney test revealed a P value of less than 0.001 for BSS group versus GT (2.4-fold) and BSS versus healthy controls (2.9-fold). CD9 molecule also expressed differently in patients with Glanzmann thrombasthenia in comparison with healthy controls (P < 0.001), although with a less magnitude (1.3-fold). According to our findings, CD9 is a potential biomarker for laboratory diagnosis of inherited glycoprotein defects, especially to elucidate the ambiguous results in BSS cases.

Perforated hemorrhagic cholecystitis in a patient with Bernard-Soulier syndrome.

Bernard-Soulier syndrome is an inherited coagulopathy, with an incidence of one per million. Hemorrhagic cholecystitis is a rare and life-threatening complication of acute cholecystitis. Less than 50 patients have been reported in the previous literature. Bleeding diathesis and anticoagulant treatment are well-known predisposing factors for hemorrhagic cholecystitis. We present a 57-year-old male patient who was referred to our department with a complaint of right upper quadrant abdominal pain. Contrast-enhanced computed tomography revealed a high-density mass associated with the gallbladder lumen, and blood clot in the gallbladder lumen and hemoperitoneum which were compatible for hemorrhagic cholecystitis and gallbladder perforation. The patient underwent urgent cholecystectomy. Hemorrhagic cholecystitis often manifests as typical acute cholecystitis presentation; but several clinical findings such as fever, lower gastrointestinal bleeding or severe intraabdominal bleeding-related hypovolemic shock may also occur. Most of the described cases in prior literature have been reported to use anticoagulant medications. This report describes the second hemorrhagic cholecystitis patient with inherited bleeding diathesis and the first case with Bernard-Soulier syndrome.

A GP1BA Variant in a Czech Family with Monoallelic Bernard-Soulier Syndrome.

Bernard-Soulier syndrome (BSS) is a rare inherited disorder characterized by unusually large platelets, low platelet count, and prolonged bleeding time. BSS is usually inherited in an autosomal recessive (AR) mode of inheritance due to a deficiency of the GPIb-IX-V complex also known as the von Willebrand factor (VWF) receptor. We investigated a family with macrothrombocytopenia, a mild bleeding tendency, slightly lowered platelet aggregation tests, and suspected autosomal dominant (AD) inheritance. We have detected a heterozygous GP1BA likely pathogenic variant, causing monoallelic BSS. A germline GP1BA gene variant (NM_000173:c.98G > A:p.C33Y), segregating with the macrothrombocytopenia, was detected by whole-exome sequencing. In silico analysis of the protein structure of the novel GPIbα variant revealed a potential structural defect, which could impact proper protein folding and subsequent binding to VWF. Flow cytometry, immunoblot, and electron microscopy demonstrated further differences between p.C33Y GP1BA carriers and healthy controls. Here, we provide a detailed insight into its clinical presentation and phenotype. Moreover, the here described case first presents an mBSS patient with two previous ischemic strokes.

Invasive procedures in the oral cavity of individuals with Bernard-Soulier syndrome: An integrative review.

AIM: Bernard-Soulier syndrome (BSS) is an inherited bleeding disorder characterized by macroplatelets and thrombocytopenia, prolonged bleeding time, and a prevalence of less than 1 in 1,000,000. In view of the recognition of the risk of bleeding and the management of daily surgical practice in these patients, adequate strategies are necessary to provide the safest care. This article aims to perform an integrative review of the literature on the management of invasive procedures in the oral cavity of individuals with BSS. METHOD: The PubMed/Medline and LILACS databases were searched using Boolean operators related to BSS, bleeding disorders, and oral care. RESULTS: As a result, only five articles with the main theme were included: one letter to the editor and four case reports, described chronologically as to date of publication, classification of the article, and medical/odontological measures taken. CONCLUSION: We conclude with this review the need for adequate knowledge of surgeons regarding coagulation disorders and the need to discuss and plan procedures with the hematology team, as well as the importance of the notion of management of possible complications resulting from invasive treatments in the oral cavity of patients with BSS.

Acquired Bernard-Soulier syndrome and hypodysfibrinogenaemia because of multiple myeloma.

We describe a case of a patient with multiple myeloma with initial presentation simulating a bleeding disorder. Detailed coagulation work-up showed hypodysfibrinogenaemia along with a platelet function defect consistent with acquired Bernard-Soulier syndrome (BSS). Multiple plasma exchanges led to significant improvement in his bleeding symptoms. To the best of our knowledge, this is the first described case of simultaneous presentation of hypodysfibrinogenaemia and BSS secondary to multiple myeloma.

Establishment of a Bernard-Soulier syndrome model in zebrafish.

Platelets play an essential role in thrombosis and hemostasis. Abnormal hemostasis can cause spontaneous or severe post-traumatic bleeding. Bernard-Soulier syndrome (BSS) is a rare inherited bleeding disorder caused by a complete quantitative deficiency in the GPIb-IX-V complex. Multiple mutations in GP9 lead to the clinical manifestations of BSS. Understanding the roles and underlying mechanisms of GP9 in thrombopoiesis and establishing a proper animal model of BSS would be valuable to understand the disease pathogenesis and to improve its medical management. Here, by using CRISPR-Cas9 technology, we created a zebrafish gp9SMU15 mutant to model human BSS. Disruption of zebrafish gp9 led to thrombocytopenia and a pronounced bleeding tendency, as well as an abnormal expansion of progenitor cells. The gp9SMU15 zebrafish can be used as a BSS animal model as the roles of GP9 in thrombocytopoiesis are highly conserved from zebrafish to mammals. Utilizing the BSS model, we verified the clinical GP9 mutations by in vivo functional assay and tested clinical drugs for their ability to increase platelets. Thus, the inherited BSS zebrafish model could be of benefit for in vivo verification of patient-derived GP9 variants of uncertain significance and for the development of potential therapeutic strategies for BSS.

A Novel Mutation in GP1BB Reveals the Role of the Cytoplasmic Domain of GPIbß in the Pathophysiology of Bernard-Soulier Syndrome and GPIb-IX Complex Assembly.

Bernard-Soulier syndrome (BSS) is an autosomal-recessive bleeding disorder caused by biallelic variants in the GP1BA, GP1BB, and GP9 genes encoding the subunits GPIbα, GPIbß, and GPIX of the GPIb-IX complex. Pathogenic variants usually affect the extracellular or transmembrane domains of the receptor subunits. We investigated a family with BSS caused by the homozygous c.528_550del (p.Arg177Serfs*124) variant in GP1BB, which is the first mutation ever identified that affects the cytoplasmic domain of GPIbß. The loss of the intracytoplasmic tail of GPIbß results in a mild form of BSS, characterized by only a moderate reduction of the GPIb-IX complex expression and mild or absent bleeding tendency. The variant induces a decrease of the total platelet expression of GPIbß; however, all of the mutant subunit expressed in platelets is correctly assembled into the GPIb-IX complex in the plasma membrane, indicating that the cytoplasmic domain of GPIbß is not involved in assembly and trafficking of the GPIb-IX receptor. Finally, the c.528_550del mutation exerts a dominant effect and causes mild macrothrombocytopenia in heterozygous individuals, as also demonstrated by the investigation of a second unrelated pedigree. The study of this novel GP1BB variant provides new information on pathophysiology of BSS and the assembly mechanisms of the GPIb-IX receptor.

Platelet features allow to differentiate immune thrombocytopenia from inherited thrombocytopenia.

Immune thrombocytopenia (ITP) is an acquired bleeding disorder, for which no specific diagnostic test exists. Inherited thrombocytopenia (IT) can mimic ITP and lead to unappropriated management with significant morbidity. Here, in small cohorts of these two disorders, we explored whether platelet sialylation and platelet activation could allow to discriminate the two conditions. We also aimed to confirm the value of immature platelet counts in this discrimination. Platelet sialylation and the expression level of P-selectin were assessed by multiparameter flow cytometry. Immature platelets were estimated on a Sysmex XN 9000 analyzer. No significant difference in platelet sialylation was observed between ITP and IT. Contrarily, platelet activation was significantly higher in ITP patients (p = 0.008). The immature platelet fraction, as previously demonstrated, was significantly lower in the ITP group compared to the IT group (p = 0.014). That statistical significance was achieved in this small pilot study suggests that the two easily available assays of immature platelet count and P-selectin expression could help physicians to reach the proper diagnosis in complex cases of thrombocytopenia.