PYGM and glycogen storage disease V: The forearm ischemia test did not show an increase in lactate and pyruvate (suggestive of McArdle's disease), and the definitive diagnosis of McArdle’s disease was established after identifying the mutations c.148C>T (p.R50X) in exon 1 and c.613G>A (p.G205S) in exon 5, both in heterozygosity in the PYGM gene.