Frequency of glycogen storage disease type II in The Netherlands: implications for diagnosis and genetic counselling

Glycogen storage disease type II (GSD II) is an autosomal recessive myopathy, Early and late-onset phenotypes are distinguished - infantile, juvenile and adult, Three mutations in the acid a-glucosidase gene are common in the Dutch patient population: IVS1(-13F-->G), 525delT and delexon18 63% of Dutch GSD II patients carry one or two of these mutations, and the genotype-phenotype correlation is known, To determine the frequency of GSD II, we have screened an unselected sample of neonates for the occurrence of these three mutations. Based on the calculated carrier frequencies, the predicted frequency of the disease is 1 in 40 000 divided by 1 in 138 000 for infantile G SD II and 1 in 57 000 for adult GSD II. This is about two to four times higher than previously suggested, which is a reason to become more familiar with the presentation of GSD II in its different clinical forms and to adjust the risk assessment for genetic counselling.