Platelet abnormalities with eosinophilia and immune-mediated inflammatory disease

A multisytem disorder caused by a variation in the ARPC1B gene, characterized by recurrent bacterial and viral infections beginning in infancy or early childhood, accompanied by inflammatory manifestations such as vasculitis, eczema, colitis, hepatosplenomegaly, and systemic autoinflammation. Affected individuals show congenital thrombocytopenia with variable platelet abnormalities including small, misshapen platelets and dense‑granule defect, and additional laboratory findings such as eosinophilia and elevated IgE or IgA. Functional studies demonstrate defects in neutrophil and T‑cell chemotaxis and impaired T‑cell activation caused by abnormal F‑actin polymerization, consistent with loss of ARPC1B function.