Elevated level of serum creatine kinase MB fraction associated with a noninflammatory myopathy. Report of a case.

A 50-year-old man had progressive, noninflammatory myopathy associated with a persistently elevated serum creatine kinase (CK) level and CK MB fraction. Possible sources of this serum CK MB include cardiac muscle, skeletal muscle, other organ sites, or occult malignant neoplasm. In our patient, lack of significant cardiovascular disease and absence of CK MB in skeletal muscle homogenate suggest another, undetermined source for serum CK MB.