CLINICAL SPECTRUM OF MYOTONIC DYSTROPHY IN CHILDREN

Objectives: To describe the phenotypical aspects of Myotonic Dystrophy (M.D) in children, and to emphasize the possibility of less severe congenital or early-onset forms compared to the classical aspects.

Methods: In a retrospective study, all cases diagnosed as M.D in Montpellier and Sherbrooke from 1994 to 2004 were analysed on a clinical point of view, with phenotype-genotype correlations as well.

Results: Beside the classical severe congenital forms of M.D, some patients can have a less serious prognosis with a slow progression, but with marked intellectual deficiency, early-onset dysmorphic features, and orthopaedic complications. Others have only a congenital weakness with hypotonia, then a motor and mental delay, with a slow progrssion. In a third group, the neonatal period is normal, but a non progressive mental deficiency remains several years the only manifestation of the disease. In these forms, the typical aspect of adult M.D appears after the age of 10 years. Finally, as in adults, the disease may have a very low progression from the age of 10, with various phenotypes (facial dysmorphy, mood disorders, myotonia ...)

Conclusion: M.D phenotype in children is extremely wide, with a continuum between the neonatal and the adult forms. No clear phenotype-genotype correlation could be made.