Spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA), popularly known as Kennedy's disease, is a rare, adult-onset, X-linked recessive lower motor neuron disease caused by trinucleotide CAG repeat expansions in exon 1 of the androgen receptor (AR) gene, which results in both loss of AR function and toxic gain of function. In men, the disease slowly progresses over decades with bulbar and lower motor neuron loss, muscle denervation, and direct skeletal muscle involvement.

Source: Wikipedia — Spinal and bulbar muscular atrophy (CC BY-SA 4.0)