[The myocardiopathies of glycogenosis].
Thirty-three patients with glycogen abnormalities and myocardial disease were studied. 27 of them has type II glycogen disorders (Pompe's disease, with an intralysozymal deficit of acid maltase) and 6 with type III glycogen disorders Forbes disease, with a deficit in amylo-1-6-glucosidase). The picture of a type II abnormality in the infant is very standard: early onset, often neonatally; the association with asystole and muscular hypotonia and a characteristics clinical picture; invariable cardiomegaly and typical ECG findings (short PR interval, high voltage complexes). Death occurs before one year of age, treatment has limited effect, and attention is centred on the early discovery of heterozygotes and of diagnosis antenatally. The possibility of an obstructive type (4 out of 24) and a type with endocardial fibroelastosis (3 out of 24) must be emphasised. In the late onset myopathic form of type II disorder (3 cases), involvement of the myocardium is always found, but is of secondary importance in determining the clinical picture and natural history. The same can be said of type III disorders in which, despite the infrequency of asystole or significant cardiomegaly, a hypertrophic cardiomyopathy which may be obstructive can lead to sudden death in infancy (2 cases out of 6).