Severe Rhabdomyolysis Without Electrolyte Abnormalities or Renal Failure and With Disproportionately Low AST

Rhabdomyolysis is a condition in which damaged muscle tissue breaks down and typically presents with muscle pain, weakness, and dark-colored urine, along with markedly elevated serum creatine kinase (CK) levels. Common lab findings include hyperkalemia, hyperphosphatemia, hypocalcemia, elevated lactate dehydrogenase (LDH), acute kidney injury (AKI), and elevated aspartate aminotransferase (AST), with a typical CK:AST ratio of approximately 20:1. This report describes a 26-year-old man with no prior medical history who developed dark urine and lower back pain after a high-intensity functional training (HIFT) session following a prolonged period of inactivity. Laboratory evaluation revealed an extraordinarily high CK of 260,100 U/L, AST of 2049 U/L, and ALT of 208 U/L, yielding a CK:AST ratio of approximately 127:1. Urinalysis showed myoglobinuria, while renal function and electrolytes remained normal throughout hospitalization. He was managed with intravenous fluids for 36 h, transitioned to oral hydration, and discharged on Day 6 with declining CK and AST levels. This case underscores that severe rhabdomyolysis may occur in the absence of renal dysfunction or electrolyte abnormalities and highlights the importance of prompt recognition and treatment even when traditional laboratory abnormalities are absent. The strikingly abnormal CK:AST ratio challenges reliance on expected lab patterns. Recognizing these atypical presentations is crucial for timely diagnosis and management. Early fluid resuscitation and close monitoring remain essential, even when routine findings appear normal.