Congenital fiber type disproportion in two sisters. A clinical and histopathological study.

Two sisters aged 27 and 29, respectively, born of nonconsanguineous parents, presented diffuse malformations at birth, followed by psychomotor retardation, reduction in muscle strength and easy fatigability at limbs. The clinical and neurophysiological examination as well as the histochemical study were indicative of a myopathic condition. Fiber type analysis in both patients showed that the type I fiber mean diameter was smaller than that of type II fibers by 12%. Clinical and laboratory findings are consistent with those observed in most cases of Congenital Fiber Type Disproportion, as described in literature.