Kennedy disease

Robert W Pratt MD ()
Louis H Weimer MD, editor. (Dr. Weimer of Columbia University has received consulting fees from Roche.)
Originally released January 15, 2005; last updated January 7, 2017; expires January 7, 2020

This article includes discussion of Kennedy disease, which is also referred to as bulbar muscular atrophy, bulbospinal muscular atrophy, bulbospinal neuronopathy, SBMA, spinal bulbar muscular atrophy, spinobulbar muscular atrophy, X-linked bulbar and spinal muscular atrophy, X-linked bulbar muscular atrophy, X-linked spinal muscular atrophy, and X-linked spinobulbar muscular atrophy. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Kennedy disease is a rare, X-linked inherited, neurodegenerative disorder characterized by a progressive weakness of the proximal limbs and bulbar muscles, muscle atrophy, fasciculations (especially perioral), loss of reflexes, tremor, gynecomastia, and diabetes mellitus. It results from an excessive number of trinucleotide (CAG) repeats in the androgen receptor gene on the X chromosome. Due to its X-linked genetic association, males are predominantly affected. Particular clinical features and genetic testing can help distinguish Kennedy disease from amyotrophic lateral sclerosis. Patients with Kennedy disease generally live a normal lifespan, despite the fact there are no treatments currently available to halt the slow progression of the disorder. In this updated article, the author summarizes the latest research on Kennedy disease, with particular emphasis on insights into its natural history, pathophysiological mechanisms, and potential therapeutic strategies.

Key points

 

• Kennedy disease is a rare, X-linked inherited, neurodegenerative disorder characterized by proximal limb and bulbar weakness, muscle atrophy, fasciculations (especially perioral), loss of reflexes, tremor, gynecomastia, and diabetes mellitus.

 

• Kennedy disease results from an excessive number of trinucleotide (CAG) repeats in the androgen receptor gene on the X chromosome.

 

• Due to its X-linked genetic association, males are predominantly affected.

 

• Particular clinical features and genetic testing can help distinguish Kennedy disease from amyotrophic lateral sclerosis.

 

• Patients with Kennedy disease often live a normal life span, although no treatments are currently available to halt the slow progression of the disorder.

Historical note and terminology

Although Kennedy disease bears the name of William R Kennedy, the first reports of this disease were likely published by LT Kurland, who described an atypical form of lower motor neuron disease in a Japanese family (Kurland 1957). Following the reports by Kurland, Magee provided additional descriptions of patients with X-linked spinobulbar muscular atrophy in the absence of corticospinal tract involvement (Magee 1960). In 1968, Kennedy reported his experience with 2 large families at the Mayo Clinic in Rochester, Minnesota (Kennedy et al 1968). The designation “Kennedy disease” was first introduced into the French literature in 1979 (Schoenen et al 1979). The disease garnered particular interest as the first example of a polyglutamine-repeat disorder, of which there are now several other neurologic examples, including Huntington disease and several of the spinocerebellar ataxias.

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