Acute kidney injury due to hemoglobin cast nephropathy secondary to autoimmune hemolytic anemia: a case report

BackgroundAutoimmune hemolytic anemia (AIHA) is an uncommon acquired disorder that can lead to life-threatening intravascular hemolysis and acute kidney injury (AKI). Hemoglobin cast nephropathy is a rare but severe complication of massive hemolysis, often underrecognized in clinical practice.Case presentationsWe describe a 57-year-old female with no prior chronic kidney disease who presented with nausea, vomiting, oliguria, edema, and rapidly progressive renal dysfunction after a presumed preceding infectious-like episode. Laboratory investigations revealed severe anemia, elevated hemolytic markers, and a positive direct antiglobulin test (DAT) for complement C3 (C3d) and negative for IgG. Renal biopsy demonstrated acute tubular injury with hemoglobin casts confirmed by immunostaining, consistent with hemoglobin cast nephropathy. The patient was treated with intermittent renal replacement therapy, intravenous methylprednisolone, and supportive care. Renal function and hemoglobin levels gradually normalized, and she remained well without relapse over 11.5 months of follow-up.ConclusionThis case highlights that when acute kidney injury and hemolytic anemia occur concurrently, hemoglobin cast nephropathy should be strongly suspected. Renal biopsy is valuable when the diagnosis is uncertain. Early immunosuppressive therapy, renal replacement therapy, and supportive care can lead to favorable outcomes.