LATE-ONSET FOOT-DROP MUSCULAR-DYSTROPHY WITH RIMMED VACUOLES

We studied a family with late-onset (fifth or sixth decade) or asympto matic hereditary myopathy of the anterior tibial muscle. The occurrenc e of the disease in two successive generations pointed out an autosoma l dominant pattern of inheritance. The initial symptom was uni- or bil ateral foot drop resembling peroneal paresis. Surprisingly many of the diagnosed patients were asymptomatic and considered themselves health y whether there was any foot drop or not. The anterior tibial muscles were atrophic in patients with foot drop but the long toe extensors we re usually and the short ones were always spared. Apparently the toe e xtensors could relieve the foot drop symptom. As shown by computed tom ography there was often an early uni- or bilateral involvement of the semimembranosus muscle in males. The proband showed also a late involv ement of the femoral biceps and the minor gluteal muscles. The muscles of the upper extremity were spared. The anterior tibial muscles had a characteristic myopathic alteration with rimmed vacuoles in histopath ological study. This picture was most evident in latent cases without atrophy of the anterior tibial muscle, but with distinctly abnormal EM G of that muscle. Non-affected muscles showed only slight non-specific histopathological changes. We suggest that this disease is a new mild variety of autosomal dominant distal myopathy with rimmed vacuoles.