Induction of heme oxygenase-1 and ferritin in the kidney in warm antibody hemolytic anemia.

Warm antibody autoimmune hemolytic anemia usually is associated with extravascular hemolysis. We report a case of a 42-year-old man with sustained and moderately severe warm antibody autoimmune hemolytic anemia, hemoglobinuria, hemosiderinuria, and acute kidney injury. We show marked induction of heme oxygenase-1 and increased ferritin expression in renal tubules, along with increased iron deposition in renal proximal tubules. These findings in this clinical case thus recapitulate those observed in experimental models of heme protein-induced kidney injury in which a coupled induction of heme oxygenase-1 and ferritin occurs in the kidney. We discuss the pathobiological significance of these findings and suggest that this linked response confers cytoprotection to the kidney exposed to hemoglobin and mitigates the severity of acute kidney injury that may otherwise occur. Finally, this case report documents that nephrotic-range proteinuria can occur in patients with autoimmune hemolytic anemia complicated by hemoglobinuria.