[Atypical hemolytic and uremic syndrome associated with von Willebrand factor-cleaving protease (ADAMTS 13) deficiency in children].

Hemolytic and uremic syndrome (HUS) is a classical form of thrombotic microangiopathies characterized by the association of hemolytic anemia with schizocytes, thrombocytopenia, and acute renal failure. Two forms of HUS have been described: the typical form that occurs after ingestion of a strain of bacteria, usually Escherichia coli types, which expresses verotoxin (also called shiga-like toxin), typically followed by bloody diarrhea, and atypical HUS, which is rare during childhood and can also be revealed by bloody diarrhea. We report a case of a 25-month-old infant who presented with hematuria and pallor after an episode of diarrhea. Biological tests revealed anemia, thrombocytopenia, and renal failure. The diagnosis of typical HUS was made, but the causal microorganism was not identified. Progression was favorable within 5 days of plasma transfusions. Two months later, the patient presented with the same symptoms and neurological impairment without any diarrhea. Von Willebrand factor-cleaving protease activity (ADAMTS 13) was low. Therefore, the diagnosis of atypical HUS by severe deficiency of ADAMTS 13 was suggested. The treatment was based on plasma transfusions resulting in remission. Atypical HUS associated with severe ADAMTS 13 deficiency rarely occurs in childhood. The prognosis, usually threatening, has been completely transformed thanks to a better understanding of the pathogenesis and to therapeutic progress.