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>T mutation in family 1 and 2, and the more recently described c.‐140C>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 (> 65 years) had lower platelet counts (<15x109L) and 1 family member with the c.‐140C>G mutation had normal platelet count in one determination. About half of the patients had Htc> 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.