Siblings with congenital thrombotic thrombocytopenic purpura.

Congenital thrombotic thrombocytopenic purpura (TTP) is a rare hereditary deficiency of ADAMTS13 (von Willebrand factor-cleaving protease) characterized by thrombocytopenia and microangiopathic hemolytic anemia. The spectrum of the clinical phenotype is wide, ranging from asymptomatic episodes of thrombocytopenia to life-threatening multiorgan failure. Reportedly, some patients develop isolated thrombocytopenia during childhood. We herein report sibling cases of congenital TTP. An 11-year-old boy with thrombocytopenia accompanied by influenza virus infection was referred to our hospital. He had a history of severe neonatal jaundice. His 15-year-old brother also had recurrent thrombocytopenia with approximately 10 episodes of recurrence since 3 years of age. Their ADAMTS13 activities were low and ADAMTS13 inhibitors were negative, and a gene analysis confirmed the diagnosis of congenital TTP. Notably, congenital TTP should be included in the differential diagnosis, and it is essential to determine the ADAMTS13 activity for pediatric patients with thrombocytopenia of unknown etiology.