JGM and may have near normal lives [2, 3] . The differential diagnosis of BMD and DMD in suspected cases is based on their clinical findings, muscle biopsy, and the mutations in DMD. Among these, positive staining for dystrophin in muscle biopsies is an important finding in the differential diagnosis [4, 5] . However, since muscle biopsies are invasive procedures, the differential diagnosis of BMD and DMD is often dependent on the mutations in DMD gene identified in the patient. According to

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... mutation database or previous reports, each DMD mutation is classified as either a DMD-or BMDcausing mutation [6] . However, when a novel DMD mutation is identified, the differential diagnosis should be based on the muscle biopsy findings along with other clinical findings. Duchenne and Becker muscular dystrophies (DMD and BMD, respectively) are X-linked neuromuscular disorders characterized by progressive muscle weakness and severe skeletal muscle degeneration. BMD is a milder form with a later onset. Patients with BMD tend to survive much longer than those with DMD. The differentiation between DMD and BMD is important in the genetic counseling of affected patients and their families. Since muscle biopsies are invasive procedures, the differential diagnosis of BMD and DMD is often dependent on the mutation identified in the DMD gene in affected patients. However, when a novel DMD mutation is identified, the differential diagnosis should be based on muscle biopsy findings with other clinical findings. Here we describe two Korean patients with BMD confirmed by muscle biopsy and genetic testing. Two novel exonic deletions in the DMD gene were identified.