Congenital hypotonia with favorable outcome.

Congenital hypotonia with favorable outcome is characterized by an early neonatal onset and a benign clinical course. The old term, proposed by Walton, was benign congenital hypotonia, denoting the presence of muscle weakness and hypotonia, with the exception of Werdnig-Hoffmann disease. It has been clear that this term includes congenital myopathies with definite changes in the muscle fiber. However, many cases remain unclarified. The term congenital hypotonia with favorable outcome includes only these last cases. A long-term follow-up study of children with congenital hypotonia with favorable outcome is presented, and a hypothetical mechanism underlying muscle shortening is discussed. The study was carried out at the Department of Child Neuropsychiatric Sciences, University "La Sapienza" of Rome, during the period 1985-2000, and included 41 patients with congenital hypotonia. Our study confirms the good prognosis of congenital hypotonia with favorable outcome and suggests a correlation with joint hyperlaxity, which is observed in many parents of our children, as if the latter developed from the former. On the basis of experimental changes occurring in the muscles, we believe that in our cohort the main cause of shortening is caused by an increase in joint mobility, which keeps muscles shortened in both the passive and active states for a long time. If this view is confirmed by other studies, we suggest continuous muscle exercise as a preventive treatment.