An undifferentiated cause of rhabdomyolysis: a case report

Rhabdomyolysis can occur secondary to infections, trauma, or myotoxic substances. Rhabdomyolysis secondary to autoimmune myositis occurs rarely. Distinguishing autoimmune rhabdomyolysis from rhabdomyolysis secondary to other causes is paramount in considering the long-term management of autoimmune rhabdomyolysis. It is further important to continue close follow-up and further testing to completely understand the extent of this disease as diagnoses may be ever-changing.

A previously healthy female presented to the hospital with myalgias and myoglobinuria following a respiratory infection treated with azithromycin and promethazine. Labs demonstrating elevated creatine kinase (CK) prompted treatment for rhabdomyolysis and rheumatology consultation. The patient was given 3 l of intravenous (IV) 0.9% sodium chloride in the Emergency Department. Upon admission, the patient was placed on a continuous IV drip of 0.9% sodium chloride running at 300 cc/hour for all 8 days of her hospital admission. The rheumatology autoantibody panel pointed towards autoimmune myositis as a potential cause of her rhabdomyolysis. The patient was discharged to follow up with rheumatology for further testing.

Autoimmune myositis, although less common than other etiologies of rhabdomyolysis, is important to consider as the long-term management of autoimmune myositis includes the use of immunosuppressants, antimalarials, or IV immunoglobulins, which may be inappropriate for other etiologies of rhabdomyolysis.