[X-chromosomal bulbospinal muscular atrophy (Kennedy syndrome)]

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 increased size of a CAG-triplet repeat on the androgen receptor gene on the X-chromosome. XBSMA is characterized by almost symmetrical muscular atrophy, 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 potentials are frequently abnormal. Additional symptoms are important for differential diagnosis, and include postural tremor, gynecomastia, diabetes mellitus, testicular atrophy and impotence. Differentiation of this hereditary disorder from treatable conditions such as multifocal motor neuropathy or amyotrophic lateral sclerosis is essential. Though life expectancy is normal, patients become disabled in the course of the disease and need supportive care. Periodic testing for diabetes is recommended, and genetic counseling should be provided for patients and their relatives.