[SBMA: a rare disease but a classic ALS mimic syndrome]

Abstract

Spinal and bulbar muscular atrophy (SBMA) is a neurodegenerative disorder of lower motor neurons characterized by proximal limb muscular atrophy, bulbar involvement, marked fasciculation, hand tremor and gynaecomastia. SBMA is caused by a CAG-repeat expansion in the androgen receptor gene on the X-chromosome. Due to its mode of transmission, only male are symptomatic and clinical features appear progressively in adulthood. Motor signs and symptoms are restricted to lower motor neuron involvement, in contrast with amyotrophic lateral sclerosis (ALS) characterized by the association with upper motor neuron involvement. The diminution of sensory potential at electroneuromyogram is a major criteria discriminating between SBMA and ALS. Diagnostic confirmation is based on genetic testing.