Atypical form of X-linked proximal pseudohypertrophic muscular dystrophy.

A series of 95 families, consisting of 317 patients with severe and mild X-linked proximal pseudohypertrophic muscular dystrophy (MD), was analysed by the use of two different and rigid clinical criteria based on the age when the patient became chairbound. Using these criteria the families from Erfurt and Warsaw could be clearly separated into classical Duchenne (DMD) and classical Becker (BMD) type patients. A third group of patients was found with atypical clinical course, who could not be identified as neither Duchenne nor Becker cases. Statistically highly significant differences were found between the groups of classical DMD and atypical MD cases on the one hand and between the groups of atypical MD and classical BMD cases on the other, especially with respect to age when chairbound and age at death. The comparisons of progression of the disease, life expectancy and of fertility between the three groups of X-linked MD show that classical DMD and atypical MD may be considered as separate types of severe X-linked proximal pseudohypertrophic MD. On the basis of these findings the authors offer conclusions for the general practice of neurology, paediatrics and genetic counseling.