Kennedy Disease – Not Quite Such a Rare Disease

Do you have male patients, aged 20 plus, presenting with weakness and atrophy of the muscles of the bulbar region and extremities?  Perhaps they also have atrophy and fibrillation of the tongue muscle, a high CK, tremor in outstretched hands, peripheral neuropathy, frequent cramps, and abnormal breast growth?

If so, they may well be living with Kennedy’s disease (also known as spinal and bulbar muscular atrophy, or SBMA); an inherited motor neuron disease that predominately affects males.  In cases where there is no known familial history, it can take many years for a definitive diagnosis to be made, undoubtedly due to a lack of awareness of the disease.  Recorded misdiagnoses include amyotrophic lateral sclerosis, spinal muscular atrophy, Guillain-Barrè syndrome, myasthenia gravis, multiple sclerosis and Parkinson’s disease.

The gold standard for diagnosis of SBMA is established in a male proband by the identification of a hemizygous expansion of a CAG trinucleotide repeat (>37 CAGs) in the Androgen Receptor (AR) gene on the X chromosome by molecular genetic testing.

In a recent UCL study the search for CAG expansion in the AR in the genomes of 74,277 unrelated individuals shows a mutation frequency of 1/3,182 X chromosomes. Based on this mutation frequency in the general population, the calculation of the prevalence of Kennedy’s disease increases to 1/6,888 males, a frequency 4.4 times greater than previously reported (1/30,303 or less).

UCLH operate a specialist Kennedy Disease Clinic at the National Hospital for Neurology and Neurosurgery.  The clinic accepts referrals for newly diagnosed Kennedy Disease patients from anywhere in the UK.

Kim Slowe

Chair of Trustees, Kennedy Disease UK

13 February 2024