Spinal and bulbar muscular atrophy (SBMA) is an adult form of X-linked motor neuron disease caused by an expansion of a CAG repeat sequence in the first exon of the androgen receptor (AR) gene.

• 脊髓延髓肌萎缩症(SBMA)是雄激素受体(AR)基因的CAG重复序列扩增引起的X连锁运动神经元病。