Kennedy's disease patients have muscle cramps and progressive weakness due to degeneration of motor neurons in the brain stem and spinal cord.
Ages of onset and severity of manifestations in affected males vary from adolescence to old age, but most commonly develop in middle adult life. The latest onset was described in a male of 84 years of age. KD does not usually compromise longevity. The syndrome has neuromuscular and endocrine manifestations.
Early signs often include weakness of tongue and mouth muscles, fasciculations, and gradually increasing weakness of limb muscles with muscle wasting. In some cases, premature muscle fatigue begins in adolescence. Neuromuscular management is supportive, and the disease progresses very slowly and often does not lead to extreme disability.
- Bulbar signs: The bulbar muscles are those supplied by the motor nerves from the brain stem, which control swallowing, breathing, speech, and other functions of the throat. Bulbar signs are problems with these muscles.
- Lower motor neuron signs: The lower motor neurons are those in the brainstem and spinal cord that directly supply the muscles. Loss of lower motor neurons leads to weakness and wasting of the muscle.
- Primary sensory neuropathy: Loss of sensation and numbness, usually not noticeable.
- Intention tremor: Hand tremor with volitional effort.
- Normal Babinski (plantar) response: When the bottom of the foot is scraped, the toes bend down. An abnormal response would be an upward movement of the toes indicating a problem with higher level (upper) motor neurons.
- Decreased or absent deep tendon reflexes: When a doctor taps the knee with his hammer little or nothing happens.
- Fasciculations: Twitching of muscles when at rest.
- Cramps: Large muscle spasms.
- Muscular atrophy: Loss of muscle bulk that occurs when the lower motor neurons do not stimulate the muscle adequately.
- Late onset: Patients usually develop symptoms in the late 30's or later.
- Slow progression: Nearly normal lifespan
- Symmetry of clinical signs: Muscles are usually affected symmetrically.
Homozygous females, both of whose X chromosomes have a mutation leading to CAG expansion of the AR gene, have been reported to show only mild symptoms of muscle cramps and twitching. No endocrinopathy has been described.
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