Differential diagnosis of high serum creatine kinase levels in systemic lupus erythematosus.

We report the clinical and bioptic findings for a 57-year-old woman with severe chloroquine-induced myopathy. Since 1989, she had been suffering from systemic lupus erythematosus (SLE) with renal involvement and undergone periods of treatment with azathioprine and cyclophosphamide. Additional therapy with chloroquine (CQ) was started because of arthralgia. At the same time, slightly increased creatine kinase (CK) levels were noted. Myositis was suspected, and the patient was treated with steroids. The CK increase persisted, however, and she developed progressive muscular weakness and muscular atrophy. Routine controls revealed markedly elevated CK levels of 1,700 U/l. The neurological and electrophysiological findings were not typical of myositis. Thus, muscle biopsy of the deltoid muscle was performed in order to exclude polymyositis or toxic myopathy. As it revealed chloroquine-induced myopathy, medication was stopped. Discriminating between primary SLE-induced affection of the musculoskeletal system and drug-induced side effects is important for appropriate treatment of SLE patients.