A new rare mutation (691delCC/insAAA) in exon 17 of the PYGM gene causing McArdle disease.

OBJECTIVE: To investigate the genetic effect of a new mutation found in exon 17 of the myophosphorylase (PYGM) gene as a cause of McArdle disease (also known as type 5 glycogenosis). Patients A Spanish patient with McArdle disease was screened for 3 common mutations in the PYGM gene (R49X, W797R, and G204S), as previously described. The patient was heterozygous for R49X. To find other mutations, the coding sequence of the entire PYGM gene was sequenced. The carrier status of his relatives was also studied. RESULTS: A novel rare mutation was found in codon 691 of exon 17. This is an insertion/deletion (indel) and consists simultaneously of a deletion of 2 bases and an insertion of 3 bases (691delCC/insAAA). A restriction analysis was designed to simplify the detection method. CONCLUSIONS: The 691delCC/insAAA is the third indel described in the PYGM gene. Indels represent 0.95% of the total reported mutations in the Human Gene Mutation Database. The molecular origin of this mutation is not fully understood. These findings point again to the allelic heterogeneity of McArdle disease.

Identification of six novel mutations in the acid alpha-glucosidase gene in three Spanish patients with infantile onset glycogen storage disease type II (Pompe disease).

Glycogen storage disease type II is an autosomal recessive muscle disorder due to deficiency of lysosomal acid alpha-glucosidase and the resulting intralysosomal accumulation of glycogen. We found six novel mutations in three Spanish classic infantile onset glycogen storage disease type II patients with involvement of both cardiac and skeletal muscle; three missense mutations (G219R, E262K, M408V), a nonsense mutation (Y191X), a donor splice site mutation (IVS18 +2gt>ga) and an in frame deletion of an asparagine residue (nt1408-1410). The missense mutations were not found in 100 normal chromosomes and therefore are not normal polymorphic variants. The splice site mutation was subsequently detected in an additional 'Spanish' infantile onset glycogen storage disease type II patient from El Salvador. Further studies will be required to determine if the IVS18 +2gt>ga splice site mutation might in fact be a relatively common Spanish mutation. Mutations among Spanish glycogen storage disease type II patients appear to be genetically heterogeneous and differ from common mutations in neighboring countries.

Unusual clinical findings and Complex III deficiency in a family with myotonic dystrophy.

Myotonic dystrophy type 1 (DM1), an autosomal dominant disease characterized by a CTG expansion in the 3' region of the DMPK gene in chromosome 19, is a highly heterogeneous disease. In this study, we present a family with early onset-classical type DM, and a homogeneous phenotype highlighted by severe neuromuscular symptoms and mental dysfunction with subcortical-type dementia. Neuroradiological abnormalities included brain atrophy, white matter lesions, and basal ganglia calcifications. A very large CTG triplet expansion was present in the DMPK locus in leukocytes in the three patients. One patient showed ragged-red fibers (RRF) and a defect complex III of the respiratory chain, but no mutations were found in the cytochrome b gene of mtDNA.