In 1968, Kennedy, Alter, and Sung described an inherited disease of progressive spinal and bulbar muscle that appeared to be found in adult males only. This became known as Kennedy's disease or X-linked bulbar spinal muscular atrophy. The mode of inheritance appears to be X-linked recessive. Symptoms often begin in previously healthy men in their 30-50s. Extra-ocular movements however are spared.
Sensory loss is often clinically undetectable.
Life span of Kennedy's disease patients may be normal, but patients can die from aspiration pneumonia. Because of the heterogeneity of symptoms of this disease, patients with Kennedy's are often initially thought to have other diseases including ALS or hereditary motor and sensory neuropathy. Reproductive function in most cases is spared. On laboratory testing, CK levels are often elevated. La Spada found that the mutation is present in the first exon in the coding area for the androgen receptor gene.