Etiological Spectrum and Histopathological Diagnosis of Rhabdomyolysis Associated Myoglobin Cast Nephropathy in South India

BACKGROUND AND AIMS: Rhabdomyolysis occurs due to injury to skeletal muscle fibers and the release of muscle constituents into the circulation. Myoglobin cast nephropathy leading to acute kidney injury is one of the most severe complications of rhabdomyolysis. This is a retrospective study which aims to analyse the clinicopathological features of myoglobin cast nephropathy. METHODS: A total of 57 cases of myoglobin cast nephropathy were identified after performing immunohistochemical staining for myoglobin on all renal biopsies with pigment casts. The clinical, laboratory data, histopathological findings and clinical outcome of these cases were evaluated. RESULTS: The mean patient age was 34.47 years (range 17-77) and the male to female ratio was 6.1:1. All patients presented with acute kidney injury with mean serum creatinine of 8.4 mg/dl (range: 1.7 to 20.8 mg/dl). Rhabdomyolysis was clinically suspected only in 31 patients. Along with myoglobin casts, acute tubular injury was present in all the biopsies. The most frequent conditions associated with myoglobin cast nephropathy in our study were snake envenomation and unaccustomed physical activities. A few activities that caused rhabdomyolysis in our patients were unique to India. CONCLUSION: Clinicians should be aware of the wide spectrum of causes for rhabdomyolysis. The classical clinical and laboratory findings of rhabdomyolysis may not be present in many of the patients. The pathologist must have a high index of suspicion, and immunohistochemical stain should be used to confirm the diagnosis.