APRIL 3, 2015
Kennedy disease, also known as spinal and bulbar muscular atrophy, is an X-linked disease, primarily affecting lower motor neurons. Affecting only men and often not presenting until the fourth decade, it is caused by a trinucleotide (CAG), polyglutamine, repeat expansion within the androgen receptor gene. Hand tremor is frequently an early manifestation, with progressive limb and bulbar weakness developing thereafter. Cramping and fasciculations are also prominent features. Electrophysiologically, up to 95% of patients with Kennedy Disease demonstrate a sensory neuronopathy with evidence of chronic denervation on EMG testing. Laboratory testing frequently reveals a hyperCKemia with levels more than 10 times normal. The presence of prominent hand tremor, perioral fasciculations and calf pseudohypertrophy help distinguish this disease from other, more progressive diseases, such as ALS and adult-onset SMA.
- Atsuna N, Watanabe H, Ito M, et al. Natural history of spinal and bulbar muscular atrophy (SBMA): a study of 223 Japanese patients. Brain 2006; 129:1446-1455.
- Ferrante MA, Wilbourn AJ. The characteristic electrodiagnostic features of Kennedy's disease. Muscle Nerve 1997; 20: 323-329.
Submitted by James Addington, MD, Resident Physician, Department of Neurology University of Virginia