[Phenotype variability in Steinert's myotonic dystrophy]

Abstract

Myotonic dystrophy, best known in the French literature as Steinert disease, is a dominantly inherited disorder. When the gene is fully expressed, it shows a characteristic clinical picture. Myopathy and myotonia are the main features, but this is a systemic disease which may involve many other organs such as the central nervous system, eyes, bones, endocrine system, etc. With the complete picture, physical and behavioral features make the diagnosis easy, only to be confirmed by neurological and ophthalmologic examination and/or electromyography. This work reviews the main clinical signs seen in the classical form of the disease. We also want to stress the variability of that picture. Finally, we describe a new dysmorphic sign in myotonic dystrophy: large prominent cupped auricles. Although not recognized, prominauris has been illustrated in a number of publications on myotonic dystrophy. Three of our adult male patients presenting the congenital form of the disease at birth have been investigated to rule out concomitant fragile-X syndrome. Both syndromes include mental retardation and dysmorphic ears. Our patients show the usual testicular atrophy, whereas the fragile-X syndrome includes testicular hypertrophy. Cytogenetic studies were normal. Old clinical description and new physical signs may lack prestige in the perspective of recent molecular biological breakthroughs, but to recognize the disease and help patients live with it will always be the role of practitioners.