Hemolysis-associated hemoglobin cast nephropathy

Hemolysis-associated hemoglobin cast nephropathy (HAHCN) is a rare cause of acute tubular injury (ATI) characterized by presence of hemoglobin casts in renal biopsy. Patients usually have extensive intravascular hemolysis evidenced by hemoglobinemia/hemoglobinuria and elevated LDH. Common causes are AIHA (autoimmune hemolytic anemia) and drugs with rifampicin in particular.

Renal biopsies in patients with HAHCN show typical pictures of an ATI with hemoglobin casts. The casts present mainly in proximal tubules and have variable appearance morphologically and tinctorially. They closely resemble myoglobin casts, another cause of ATI. Immunohistochemical study is needed to differentiate between the two. RBC casts can be differentiated from hemoglobin casts based on light microscopy. In spite of positive hemoglobin staining, RBC casts contain degenerated "ghost" RBCs. Renal injury by HAHCN is supposed to be due to decreased renal perfusion, direct toxic injury to tubular cells and tubular obstruction.

Renal injury in HAHCN is reversible if the cause of hemolysis is eliminated.

Dvanajscak Z, Walker PD, Cossey LN, et al. Hemolysis-associated hemoglobin cast nephropathy results from a range of clinicopathologic disorders. Kidney Int. 2019;96(6):1400‐1407. doi:10.1016/j.kint.2019.08.026