Continued need for caution in the diagnosis of Duchenne muscular dystrophy

The article by Schwartz et al. in this issue of Neurology emphasizes information important to the clinical and molecular diagnosis of limb-girdle (LGMD), Duchenne (DMD), and Becker (BMD) muscular dystrophies. They report that 13 out of their 102 patients previously diagnosed with sporadic DMD actually have one of the commoner forms of LGMD—LGMD type 2I—a disorder that is caused by mutations in the fukutin-related protein gene.1 The implications of the report are that many if not most previous clinical articles on DMD and BMD where the molecular diagnosis was not confirmed will have included patients with this disease. While a DMD-like phenotype has been identified in other studies of LGMD2I,2 the surprisingly large percentage of such cases in the current article has important implications for diagnosis, genetic counseling, and clinical trials. …