PB2614: MISDIAGNOSIS OF PRIMARY IMMUNE THROMBOCYTOPENIA IN THE COMMUNITY SETTING AND ITS ASSOCIATION WITH INHERITED PLATELET DISORDERS: REPORTING NEW VARIANTS OF INHERITED PLATELET DISORDERS

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Topic: 32. Platelet disorders Background: Primary immune thrombocytopenia (ITP) is an acquired immune-mediated disease that typically presents with thrombocytopenia and a wide range of bleeding manifestations. The incidence of ITP is estimated to be 1.6 to 3.0 per 100,000 people per year in adults. The diagnosis of ITP can be challenging to make due to the heterogeneity of clinical presentation and the lack of a specific diagnostic test. Despite the 2009 international ITP working group standard definition of ITP as a platelet count <100 x109/ L with no known etiology, the misdiagnosis has remained an issue since the criteria lack sensitivity and specificity leading to inappropriate treatments such as splenectomy and toxic immunosuppressive medications. It is not uncommon for patients with such misdiagnosis to be referred to large academic centers as refractory ITP, and at that time, a different diagnosis is established. Aims: We aim to identify the percentage of patients with the misdiagnosis of ITP and its association with inherited platelet disorders with the intention of educating community providers and preventing inappropriate treatments. We also like to report novel mutations in inherited thrombocytopenic disorders and their association with clinical syndromes. Methods: We report a single-center experience here at the University of Southern California- Kenneth Norris Comprehensive Cancer Center (KNCCC) evaluating community referrals for ITP/refractory ITP and the percentage of misdiagnosis. Analysis of referrals to two clinicians at the KNCCC over the last ten years was evaluated with a total number of fifty-nine (n=59) referrals. Data collected included demographics, family history, bleeding history, basic laboratory including complete blood count including differential and mean platelet volume, complete metabolic panel, platelet aggregation studies, cytogenetics studies, and fulgent 44 gene platelet panel. The percentage of misdiagnosis was recorded, and a PubMed search with different gene variants was conducted to determine if mutations had been previously reported. Results: A total number of fifty-nine (n=59) referrals were obtained over the last ten years. Eight out of fifty-nine (~14%) were incorrectly diagnosed as ITP. Two out of the fifty-nine patients had an actual diagnosis of myelodysplastic syndrome (MDS), and six out of the fifty-nine patients had an inherited platelet disorder, some with new genetic variants that were clinically significant. A table of the patients with inherited platelet disorders with reported gene mutation, including some not reported in the literature, can be seen in Table 1. Summary/Conclusion: Immune thrombocytopenia is a diagnosis of exclusion that can be difficult to make due to the lack of a sensitive and specific test. Based on our single-center experience, ~14% (n=8) of patients who were referred from the community had a misdiagnosis of ITP. The most common diagnosis was inherited platelet disorders accounting for 10% of the misdiagnosis, followed by MDS. Our experience demonstrates the importance of obtaining a thorough clinical history, the importance of reviewing peripheral smears, and the utility of genetic testing when there is a high index of suspicion. This is important not only to prevent misdiagnosis and unnecessary treatment, but many inherited platelet disorders carry a risk of clinical syndromes such as myeloid malignancies and clinically significant bleeding.Keywords: Thrombocytopenia, Platelet aggregation, Bernard-Soulier syndrome, Immune thrombocytopenia (ITP)

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