Thrombocytopenia 3

An inherited thrombocytopenia caused by a variation in the FYB1 gene, characterized by small-platelet thrombocytopenia beginning in infancy, with variable mucocutaneous bleeding including petechiae, epistaxis, and heavy menstrual bleeding. Platelet studies in affected individuals reveal reduced pseudopodia formation, impaired integrin activation, increased basal P-selectin and PAC-1 expression, and reduced ability to upregulate activation markers following ADP stimulation. Megakaryocyte abnormalities, including reduced numbers of mature multilobulated megakaryocytes and impaired proplatelet development, reflect a defect in cytoskeletal organization linked to the loss of FYB1's adaptor function in integrin-mediated signaling.