Schwartz-Jampel syndrome. Clinical, electrophysiological and histopathological study of a severe variant.

This report describes a child, offspring of a first cousin marriage, with a severe and progressive disorder of bone and cartilage growth associated with a myotonia-like syndrome. Clinical manifestations of this disease began at birth with marked generalized muscle hypertrophy, stiffness, myotonia and multiple skeletal deformities. Successively severe dwarfism and mental retardation were observed. Neurophysiological studies showed continuous high frequently low voltage activity at rest and myotonic discharges which did not wax and wane. These abnormalities persisted after complete curarization. Muscle biopsy showed mild dystrophic changes. Polymeric glycosaminoglycans and degradation product excretion was normal. These findings are similar to those described in Schwartz-Jampel syndrome, but since the clinical picture was fully expressed at birth and was unusually severe, it is suggested that the patient's condition may have represented a severe variant of this syndrome.