X-LINKED BULBOSPINAL MUSCULAR-ATROPHY (KE NNEDYS-DISEASE)

Two brothers with slowly progressive weakness and congenital nystagmus are presented. DNA analysis confirmed X-linked recessive bulbospinal muscular atrophy (XBSMA, Kennedy's disease) by demonstration of increa sed size of a CAG-triplet repeat on the androgen receptor gene on the X-chromosome. XBSMA is characterized by almost symmetrical muscular at rophy, weakness and fasciculations predominantly of bulbar, facial and proximal muscles of the extremities, with onset in the third to fifth decade. Tendon reflexes are depressed and pyramidal signs are absent. Sensory symptoms are clinically rare, but sensory nerve action potent ials are frequently abnormal. Additional symptoms are important for di fferential diagnosis, and include postural tremor, gynecomastia, diabe tes mellitus, testicular atrophy and impotence. Differentiation of thi s hereditary disorder from treatable conditions such as multifocal mot or neuropathy or amyotrophic lateral sclerosis is essential. Though li fe expectancy is normal, patients become disabled in the course of the disease and need supportive care. Periodic testing for diabetes is re commended, and genetic counselling should be provided for patients and their relatives.