In a retrospective study, 32 patients with myotonic dystrophy, including congenital (n=17) and infantile/juvenile forms (n=15) were studied during a long follow-up lasting 7-28 years (median: 17 years). The clinical presentation was extremely variable; however, a continuum did exist between severe and less severe congenital forms, and later-onset forms, without genotype-phenotype correlation. We observed some unusual presentations, such as 3 cases of isolated club-feet during the neonatal period, and 7 patients (23%) with a completely isolated mental deficiency, language delay and school failure, who only completed the clinical picture several years later. Wechsler scale testing was performed in all cases, and repeated with 8 patients. It demonstrated a decrease in intellectual abilities in 5 patients, suggesting the possibility of a degenerative cerebral process occurring in these children. This decrease has also been reported in some adult cases. This study illustrates the extremely heterogeneous clinical presentation of myotonic dystrophy in childhood.