A case of thrombotic microangiopathy in a patient with permanently low haptoglobin expression

Abstract

Haptoglobin (Hp) is required for the metabolism of hemoglobin into bilirubin after hemolysis. Herein, we report a case of thrombotic microangiopathy (TMA) in a person with permanently low expression of Hp. The patient was an 80‒year‒old man. He was referred to our hospital because of rapid deterioration of renal function within a few days. The patient had thrombocytopenia, anemia with schistocytes, elevated LDH, and his serum Hp level was below detection sensitivity. During the course of blood transfusion and hemodialysis as supportive care, TMA subsided. The patient was weaned from hemodialysis. Two years after discharge, plasma Hp concentration remained below the detection sensitivity of conventional nephelometry and was barely detectable by high‒sensitivity ELISA. The absence of jaundice during the acute phase of TMA was likely due to low Hp expression. When such an atypical sign is observed in TMA in the future, congenital Hp deficiency should be considered. Special precautions against anaphylaxis are recommended during transfusion and plasma exchange, which may become the preferred treatment options.