Intravenous gamma globulin for thrombotic microangiopathy of unknown etiology.

We encountered the case of a 4-year-old boy with thrombotic microangiopathy (TMA) of unknown etiology. Verotoxin-induced hemolytic uremic syndrome (HUS), Streptococcus-pneumoniae-related HUS, factor H deficiency, drug-induced thrombotic thrombocytopenic purpura (TTP), and ADAMTS13 (von Willebrand factor-cleaving protease; a disintegrin-like and metalloprotease with thrombospondin type 1 repeats)-related TTP were excluded. His condition was refractory to anticoagulants and plasma exchange, and his clinical course was catastrophic, with central nervous system symptoms and progressive renal failure.