RESUMEN
Glycogen storage disease type V (GSD-V) is the most common disorder of muscle glycogenosis with characteristic clinical and laboratory findings. A 32-yr-old woman complained of exercise intolerance and myoglobulinuria since early adolescence. She reported several episodes of second-wind phenomenon. Physical examination did not show any neurological abnormality, including fixed muscle weakness or atrophy. Serum creatine kinase level was 1,161 IU/L at rest. The result of the non-ischemic forearm exercise test was compatible with GSD-V. Mutation analysis identified the compound heterozygous mutations of the PYGM, p.D510fs and p.F710del, which has not yet been reported in Korea. The present case recognizes that detail clinical and laboratory analysis is the first step in the diagnosis of GSD-V.