A missense mutation W797R 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 T-to-C transi tion results in the replacement of a highly conserved tryptophan at amino a cid position (aa) 797 with an arginine in the C-terminal domain of the PYGM protein. The lack of enzyme activity in the proband's muscle is consistent with a crucial role of the aa 797 in the normal function of the PYGM prote in. Our data further expand the genetic heterogeneity in patients with McAr dle's disease. (C) 2000 John Wiley & Sons, Inc.