Atypical Biopsy-Proven Myoglobin-Induced Acute Tubular Injury in the Setting of Normal Creatine Phosphokinase and Urine Myoglobin

Rhabdomyolysis can be complicated by acute kidney injury due to myoglobin-induced nephrotoxicity and tubular injury, in addition to volume depletion related to fluid sequestration. It is, however, unusual to have acute kidney injury with normal creatine phosphokinase (CPK) and negative urine myoglobin. We present an atypical case in which a 66-year-old woman presented with acute renal failure of unclear etiology, which required temporary dialysis support. After extensive evaluation, a renal biopsy was conclusive for myoglobin-induced tubular injury. This patient had received an influenza vaccine one month prior to her presentation, which was complicated by severe myalgias, suggesting that she had significant rhabdomyolysis in the initial days following the vaccination, which led to the acute kidney injury. CPK was normal and urine myoglobin was negative at the time of presentation, one month following vaccination. This is an uncommon presentation of rhabdomyolysis and acute kidney injury and demonstrates that acute kidney injury due to rhabdomyolysis can have a delayed presentation, which can be confirmed by kidney biopsy findings of acute tubular injury with myoglobin staining casts.