Myoglobin Casts

A 54-year-old man with a history of hypertension and hypercholesterolemia presented with complaints of generalized “muscle stiffness” and cola-colored urine. He was found to have markedly elevated serum creatinine and creatine kinase levels. A renal biopsy showed acute tubular injury with numerous pigmented casts (Fig 1), which were proven to be myoglobin casts by immunohistochemistry (Fig 2). The etiology of the patient’s myoglobinuria was thought to be statin medication, the dose of which had recently been increased. Here is a link to a recent article describing the morphologic spectrum of myoglobin casts in renal biopsies:https://www.ncbi.nlm.nih.gov/pubmed/?term=27038680.