TIBIAL MUSCULAR-DYSTROPHY - LATE ADULT-ONSET DISTAL MYOPATHY IN 66 FINNISH PATIENTS

Objective.-To clarify the classification of two previously reported gr oups of patients with anterior tibial distal dystrophy, to find additi onal patients with the disease, and to describe the clinical features of this disease. Design.-National survey of the records of patients wi th neuromuscular diseases in Finland. Findings of selected patients we re compared with those of previously reported cases. Patients.-Thirty- six previously described patients and 30 additional patients from the current survey, with 41 symptomatic patients and 25 subjectively asymp tomatic affected relatives. Results.-There were 66 patients with late adult-onset tibial muscular dystrophy. Symptoms appear after the age o f 35 years with reduced ankle dorsiflexion, and progress is slow witho ut marked disability. Facial muscles, upper extremities, and proximal muscles are usually spared. Muscle biopsy results reveal nonspecific d ystrophic changes in clinically affected muscles, and frequently sever e adipose replacement in the anterior tibial muscles occurs. Asymptoma tic muscles have mild myopathic changes only. Vacuolar degeneration is detected in a minority of patients. Electromyography shows profound m yopathic changes in the anterior tibial muscle, but extensor brevis mu scles are well preserved. Computed tomography or magnetic resonance im aging of muscles discloses marked involvement of tibial extensor muscl es and focal patches of fatty degeneration in various asymptomatic mus cles. Pedigree data suggest autosomal dominant inheritance. Conclusion s.-Tibial muscular dystrophy might represent a new form of distal myop athy and it is rather common, at least in Finland.