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Platelets play a fundamental role in normal hemostasis, while their inherited or acquired dysfunctions are involved in a variety of bleeding disorders or thrombotic events. Several laboratory methodologies or point-of-care testing methods are currently available for clinical and experimental settings. These methods describe different aspects of platelet function based on platelet aggregation, platelet adhesion, the viscoelastic properties during clot formation, the evaluation of thromboxane metabolism or certain flow cytometry techniques. Platelet aggregometry is applied in different clinical settings as monitoring response to antiplatelet therapies, the assessment of perioperative bleeding risk, the diagnosis of inherited bleeding disorders or in transfusion medicine. The rationale for platelet function-driven antiplatelet therapy was based on the result of several studies on patients undergoing percutaneous coronary intervention (PCI), where an association between high platelet reactivity despite P2Y12 inhibition and ischemic events as stent thrombosis or cardiovascular death was found. However, recent large scale randomized, controlled trials have consistently failed to demonstrate a benefit of personalised antiplatelet therapy based on platelet function testing.

Platelets play a major role in hemostasis as ppwell as in many other physiological and pathological processes. Accordingly, production of about 1011 platelet per day as well as appropriate survival and functions are life essential events. Inherited platelet disorders (IPDs), affecting either platelet count or platelet functions, comprise a heterogenous group of about sixty rare diseases caused by molecular anomalies in many culprit genes. Their clinical relevance is highly variable according to the specific disease and even within the same type, ranging from almost negligible to life-threatening. Mucocutaneous bleeding diathesis (epistaxis, gum bleeding, purpura, menorrhagia), but also multisystemic disorders and/or malignancy comprise the clinical spectrum of IPDs. The early and accurate diagnosis of IPDs and a close patient medical follow-up is of great importance. A genotype–phenotype relationship in many IPDs makes a molecular diagnosis especially relevant to proper clinical management. Genetic diagnosis of IPDs has been greatly facilitated by the introduction of high throughput sequencing (HTS) techniques into mainstream investigation practice in these diseases. However, there are still unsolved ethical concerns on general genetic investigations. Patients should be informed and comprehend the potential implications of their genetic analysis. Unlike the progress in diagnosis, there have been no major advances in the clinical management of IPDs. Educational and preventive measures, few hemostatic drugs, platelet transfusions, thrombopoietin receptor agonists, and in life-threatening IPDs, allogeneic hematopoietic stem cell transplantation are therapeutic possibilities. Gene therapy may be a future option. Regular follow-up by a specialized hematology service with multidisciplinary support especially for syndromic IPDs is mandatory.

Flow cytometric platelet activation has emerged as an alternative diagnostic test for inherited platelet disorders. It is, however, labor intensive and few studies have directly compared the performance of flow cytometric platelet activation (PACT) to light transmission aggregometry (LTA). The aims of this study were 1/ to develop a simplified flow cytometric platelet activation assay using microtiter plates and 2/ to correlate the outcome to gold standard method LTA, and to clinical bleeding assessment tool scores (BAT score). The PACT method was developed in microtiter plates using adenosine diphosphate (ADP), collagen-derived peptide (CRP-XL) and thrombin receptor activator for peptide 6 (TRAP-6) as agonists. Antibodies against GPIIb-IIIa activation epitope (PAC1), P-selectin (CD62P) and lysosome-associated membrane glycoprotein 3 (LAMP3; CD63) were used as platelet activation markers. Sixty-six patients referred to the coagulation unit for bleeding symptoms were included in this single-center observational study. Platelet activation was determined by PACT and LTA. The results of both methods were correlated to BAT score. A two-by-two analysis using Cohen's kappa analysis gave moderate agreement between LTA and PACT (82%, kappa = 0.57), when PACT analysis with ADP and CRP-XL was compared to LTA. Using LTA as reference method, positive predictive value was 70% and negative predictive value was 87%. A substantial number of patients had high BAT score and normal LTA and PACT results. Patients with abnormal LTA or PACT results had higher BAT score than patients with normal results, but the difference was not significant. The performance in microtiter plates simplified the PACT method and enabled analysis of more patients at the same time. Our results indicate that with modification of the current PACT assay, a higher negative predictive value can be obtained. Furthermore, with comparable result to LTA the PACT could be used as a screening assay for inherited platelet disorders.

Inherited platelet function disorders (IPFD) are characterized by normal platelet count and morphology but impaired function due to pathogenic variants in genes encoding membrane receptors, granule constituents, or intracellular signaling proteins. Glanzmann’s thrombasthenia, the most representative IPFD, results from ITGA2B or ITGB3 mutations that disrupt the αIIbβ3 integrin complex, producing severe mucocutaneous bleeding. Advances in molecular genetics have expanded the IPFDs landscape to include defects in other platelet receptors (Glycoprotein (GP)-VI, P2Y12, and thromboxane A2[TxA2]-R), signaling mediators (RASGRP2, FERMT3, G-protein regulators, PLC, and TxA2 pathway enzymes), and granule biogenesis disorders such as Hermansky–Pudlak and Chediak–Higashi syndromes. High-throughput sequencing technologies, including long-read approaches, have greatly improved diagnostic yield and clarified genotype–phenotype correlations. Clinically, bleeding severity varies from mild to life-threatening, and management relies on antifibrinolytics, desmopressin, or platelet transfusion; recombinant activated factor VII and hematopoietic stem cell transplantation are reserved for selected cases. Emerging strategies such as gene therapy and bispecific antibodies that link platelets and coagulation factors represent promising advances toward targeted and preventive treatment. A better knowledge of the clinical features and understanding molecular pathogenesis of IPFDs not only enhances diagnostic precision and therapeutic options but also provides key insights into platelet biology, intracellular signaling, and the broader mechanisms of human hemostasis.

Lassa fever (LF) causes multisystem disease and has a fatality rate <70%. Severe cases exhibit abnormal coagulation, endothelial barrier disruption, and dysfunctional platelet aggregation but the underlying mechanisms remain poorly understood. In Sierra Leone during 2015-2018, we assessed LF patients' day-of-admission plasma samples for levels of proteins necessary for coagulation, fibrinolysis, and platelet function. P-selectin, soluble endothelial protein C receptor, soluble thrombomodulin, plasminogen activator inhibitor 1, ADAMTS-13, von Willebrand factor, tissue factor, soluble intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 were more elevated in LF patients than in controls. Endothelial protein C receptor, thrombomodulin, intercellular adhesion molecule 1, plasminogen activator inhibitor 1, D-dimer, and hepatocyte growth factor were higher in fatal than nonfatal LF cases. Platelet disaggregation occurred only in samples from fatal LF cases. The impaired homeostasis and platelet dysfunction implicate alterations in the protein C pathway, which might contribute to the loss of endothelial barrier function in fatal infections.

Rare pathogenic variants in either the ITGA2B or ITGB3 genes have been linked to autosomal dominant macrothrombocytopenia associated with abnormal platelet production and function, deserving the designation of Glanzmann Thrombasthenia-Like Syndrome (GTLS) or ITGA2B/ITGB3-related thrombocytopenia. To describe a series of patients with familial macrothrombocytopenia and decreased expression of [alpha]IIb[beta]3 integrin due to defects in the ITGA2B or ITGB3 genes. We reviewed the clinical and laboratory records of 10 Portuguese families with GTLS (33 patients and 11 unaffected relatives), including the functional and genetic defects. Previously reported ITGA2B and ITGB3 variants related to thrombocytopenia were clustered in a confined region of the membrane-proximal cytoplasmic domains, the inner membrane clasp. For the first time, variants are reported at the outer membrane clasp, at the transmembrane domain of [alpha]IIb, and at the membrane distal cytoplasmic domains of [beta]3. This is the largest single-center series of inherited macrothrombocytopenia associated with [alpha]IIb[beta]3 variants published to date.

Inherited platelet disorders (IPDs) are a group of rare conditions affecting platelet number, function, or both. Clinical manifestations vary widely, from asymptomatic cases to patients with severe bleeding, syndromic features, or early-onset blood cancers. Some are diagnosed due to family history. Early and accurate diagnosis—through both clinical and molecular evaluation—is essential for effective patient management and to avoid inappropriate treatments due to misdiagnosis. Genetic confirmation aids in prognosis, follow-up planning, family screening, genetic counseling, and donor selection for stem cell transplantation if required. However, diagnosing IPD is still challenging due to the disorders’ complexity and the limitations of current lab tests. This review outlines the diagnostic process for IPD and provides evidence-based, practical recommendations informed by scientific literature and clinical experience.

MicroRNAs (miRNAs) are small RNA molecules that modulate gene and protein expression in hematopoiesis. Platelets are known to contain a fully functional miRNA machinery. While platelets used for transfusion are normally stored at room temperature, recent evidence suggests more favorable effects under a cold-storage condition, including higher adhesion and aggregation properties. Thus, we sought to determine whether functional differences in platelets are associated with the differential profiling of platelet miRNA expressions. To obtain the miRNA expression profile, next-generation sequencing was performed on human platelets obtained from 10 healthy subjects. The miRNAs were quantified after being stored in three different conditions: 1) baseline (before storage), 2) stored at 22°C with agitation for 72 h, and 3) stored at 4°C for 72 h. Following the identification of miRNAs by sequencing, the results were validated at the level of mature miRNAs from 18 healthy subjects, by using quantitative polymerase chain reaction (qPCR). Differential expression was observed for 125 miRNAs that were stored at 4°C and 9 miRNAs stored at 22°C as compared to the baseline. The validation study by qPCR confirmed that storage at 4°C increased the expression levels (fold change 95% CI) of mir-20a-5p (1.87, p<0.0001), mir-10a-3p (1.88, p<0.0001), mir-16-2-3p (1.54, p<0.01), and mir-223-5p (1.38, p<0.05), compared with those of the samples stored at 22°C. These results show that miRNAs correlate with platelet quality under specific storage conditions. The data indicate that miRNAs could be potentially used as biomarkers of platelet quality.

Inherited platelet function disorders (IPFDs) are rare diseases caused by defects in platelet surface receptors, enzymes, granules, or signaling proteins. In humans, GPVI and P2Y12 deficiency cause autosomal recessive bleeding disorders, while TBXAS1 deficiency is related to Ghosal hematodiaphyseal dysplasa, a rare autosomal recessive disorder characterized by increased long bone density and platelet dysfunction without bleeding. To date, at least 20 patients have been identified with molecular defects in P2RY12, 12 cases with molecular defects in GP6, and 34 cases with molecular defects in TBXAS1. Here, we report a novel nonsense and missense variants in P2RY12, a novel nonsense variant in GP6, and a novel missense variant in TBXAS1. These variants selectively affect the platelet reactivity to ADP and collagen/CRP, predisposing to bleeding. P2RY12 c.835 G>A [p.Val279Met] variant did not affect receptor expression whereas P2RY12 c.44delG [p.Ser15Ilefs*33] lead to decreased levels of the receptor in one of the patients. This was confirmed both by RT-qPCR and immunoblotting analysis. Decreased expression of both GPVI and FcRγ-chain was detected in patients carrying GPVI nonsense variant in heterozygosis. The deleterious effect of these variants was also confirmed in a transfected cell line model. TBXAS1 variant triggered decreased TxA2 production using a cell line model. These variants expand the genetic landscape of P2RY12, GPVI and TBXAS1 inherited deficiency.

Background Severe fever with thrombocytopenia syndrome (SFTS) is emerging in Asian 3 countries, China, Japan and Korea, which are scrub typhus endemic areas, and its incidence is increasing. As the two infections overlap epidemiologically and clinically and the accessibility or sensitivity of diagnostic tests is limited, early clinical prediction may be useful for diagnostic and therapeutic purposes. Methods Patients aged ≥16 years who were clinically suspected and laboratory-confirmed to be infected with Orientia tsutsugamushi or the SFTS virus in South Korea were enrolled. Clinical and laboratory parameters were compared. Scrub typhus was further subclassified according to the status of eschar and skin rash. An SFTS prediction scoring tool was generated based on a logistic regression analysis of SFTS compared with scrub typhus. Results The analysis was performed on 255 patients with scrub typhus and 107 patients with SFTS. At initial presentation, subjective symptoms except for gastrointestinal symptoms, were more prominent in scrub typhus patients. In addition to the characteristic eschar and skin rash, headache was significantly more prominent in scrub typhus, while laboratory abnormalities were more prominent in SFTS. Leukopenia (white blood cell count < 4000/mm 3 ; odds ratio [OR] 30.13), thrombocytopenia (platelet count < 80,000 /mm 3 ; OR 19.73) and low C-reactive protein (< 1 mg/dL; OR 67.46) were consistent risk factors for SFTS (all P  < 0.001). A prediction score was generated using these 3 variables, and a score ≥ 2 had a sensitivity of 93.1% (95% confidence interval [CI], 87.9–96.4%) and a specificity of 96.1% (95% CI, 93.8–97.6%) for SFTS. Conclusion This prediction scoring tool may be useful for differentiating SFTS from eschar- or skin rash-negative scrub typhus. It is a simple and readily applicable tool with potential for use in primary care settings.