A homozygous missense mutation (A659D) in the myophosphorylase gene in a Spanish patient with McArdle's disease.

We identified a novel missense mutation in the myophosphorylase gene (PYGM) in a Spanish patient with McArdle's disease. This homozygous C-to-A mutation results in the replacement of a highly conserved alanine at amino acid position 659 with an aspartic acid in the C-terminal domain of the myophosphorylase gene protein, near binding sites for pyridoxal phosphate and glucose. Our data further expand the genetic heterogeneity in patients with McArdle's disease.