Hemoglobin casts in kidney biopsies: Etiological spectrum

Intravascular hemolysis, which is the destruction of red blood cells in circulation, can cause acute kidney injury as the hemoglobin released by the lysed cells is toxic to the tubular epithelial cells. We performed a retrospective analysis of 56 cases of hemoglobin cast nephropathy reported at our institution to analyze the etiological spectrum causing this rare disease. The mean patient age was 41.7 (range: 2-72 years), and the male-to-female ratio was 1.8:1. All patients presented with acute kidney injury. The etiologies include rifampicin-induced, snake bite, autoimmune hemolytic anemia, falciparum malarial infection, leptospiral infection, autoimmune hemolytic anemia, sepsis, non-steroidal anti-inflammatory drugs, ingestion of termite oil, heavy metal poisoning, wasp sting, and valvular heart disease with severe mitral regurgitation. We demonstrate a wide spectrum of conditions associated with hemoglobin casts in the kidney biopsy. Hemoglobin immunostain is required to establish the diagnosis.