A Thai 37 years old man presented with adult onset progressive proximal muscle weakness and generalized
myalgia. Family history showed similar symptoms in several male relatives, compatible with X-linked recessive inheritane.
Electromyography suggested myopathic process. Serum creatine kinase was highly elevated. Diagnosis of Becker muscular
dystrophy (BMD) was confirmed by genetic testing. His symptoms responded well to steroid treatment. This report is of the
first Thai patient with atypical presentation of BMD.

Keyword: Dystrophin, Myalgia, X-linked