Serum creatine kinase BB and MM concentrations determined by radioimmunoassay in neuromuscular disorders

We measured the MM and BB isoenzymes of serum creatine kinase (CK) by radioimmunoassay in 89 patients with neuromuscular disorders and 44 definite or possible carriers of Duchenne muscular dystrophy (DMD). The CK-MM isoenzyme was closely associated with total CK enzymatic activity. CK-BB was not as closely correlated with total CK but was usually increased in the inflammatory myopathies and DMD and normal in myasthenia gravis, Guillain-Barré syndrome, and amyotrophic lateral sclerosis as well as in neuropathies in which CK is usually normal. In myopathies, CK-BB may be useful for assessing the level of disease activity or the regenerative component. More study is necessary to assess the role of CK-BB in detection of DMD carriers.