An Unusual Patient with Atypical Hemolytic Uremic Syndrome Who Developed Hemophagocytic Lymphohistiocytosis

Hemolytic uremic syndrome (HUS) is characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia and acute renal failure. Atypical HUS is characterized by the absence of antecedent diarrhea, tendency to relapse, a positive family history and poor therapeutic outcome. Here we report an 8-year-old boy who presented with atypical HUS and did not have antecedent diarrhea or infection. He developed prolonged fever unresponsive to broad-spectrum antibiotics with markedly elevated liver enzymes and hepatosplenomegaly. There were phagocytized macrophages in his bone marrow aspiration. Based on these observations and other laboratory fi ndings, he was diagnosed with hemophagocytic lymphohistiocytosis. He was successfully treated with plasma exchanges and low dose oral steroids. To our knowledge, this is the fi rst case of atypical HUS in the literature associated with hemophagocytic lymphohistiocytosis.