Myalgia and cramps: dystrophinopathy with wide-ranging laboratory findings

We present 12 cases of males with myalgia and cramps and a normal muscle strength examination. All the patients had muscle dystrophin values consistent with Becker muscular dystrophy. Five of the patients had a normal electromyogram, and five had normal light microscopic muscle biopsy results. Of particular note, four of the 12 patients had normal serum creatine kinase levels, and four others had only mild elevations (less than twice the upper limit of normal). These patients establish an identifiable dystrophinopathy of adolescent boys and young men that can present with muscle pain and, in some cases, normal routine laboratory evaluations.