Kennedy disease is a rare inherited motor neuron disease that affects men. It is a lower motor neuron disease involving disruptions in the transmission of nerve cell signals, resulting in progressive muscle weakness and cramps.
Also known as spinal and bulbar muscular atrophy, the disease usually only becomes apparent in adult life.
It is characterised by the degeneration of lower motor neurons within the spinal cord and brainstem, resulting in muscle weakness and cramps in the arms, legs and facial area. There may be difficulty speaking and swallowing (dysphagia).
It could lead eventually to lack of mobility and to a need for full-time care. Life expectancy, however, is normal.
Causes
Kennedy’s disease is caused by a genetic mutation of the androgen receptor gene on the X chromosome.
Boys have an X chromosome, which comes from their mother, and a Y chromosome, which comes from their father, while girls have two X chromosomes, one from each parent.
With girls the defect on one of the X chromosomes is overridden by the normal X chromosome, which is why the defect normally only affects males. Girls can, however, be carriers of the disease and pass it onto their male offspring when they grow up and have children.
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A man who has Kennedy’s disease may pass the disease onto his daughters, who will be carriers of the defective gene but not suffer from the disease themselves. He will not pass it onto his sons, since he will only be contributing the Y chromosome to them.
A woman who is a carrier of the disease has a 50 percent chance of passing it onto her son.
Symptoms
Neurological symptoms usually start between the ages of 20 and 50. The disease affects the lower motor neurons that are responsible for the movement of many muscles in the legs, arms, mouth and throat.
Early symptoms include a tremor in outstretched hands, muscle cramps with exertion and muscle twitches under the skin.
Eventually there is limb weakness beginning usually in the pelvic or shoulder regions and extending to arm and leg muscles, where the symptoms may be weakness or cramps. There may also be numbness.
Later facial, mouth and tongue muscles may become weak, as the disease progresses. This may lead to difficulty in swallowing (dysphagia), slurred speech (dysarthria) and recurrent aspiration pneumonia.
Neurons which connect the spinal cord to the muscles, become defective and die, so the muscles cannot contract. The destruction of these nerves is the main reason for the numbness, muscle weakness and inability to control muscle contraction.
There may be twitching and trembling in certain positions. Some men may develop gynecomastia (excessive enlargement of male breasts) and a low sperm count or infertility.
Others develop non-insulin-dependent diabetes mellitus. Testicular atrophy, which is a shrinking of the testicles, may also occur.
With lack of normal neuromuscular function, a patient may experience hypertrophied calves in which the calf muscles thicken due to muscle cramps. In some cases, one side of the body may be more affected than the other.
Leg muscular weakening can cause walking difficulties and a propensity to fall.
Arm and leg muscle loss causes cramping.
Bulbar muscles in the face and throat are also impacted, which leads progressively to difficulty in swallowing and speaking impairment.
Diagnosis
Due to its rarity, Kennedy's disease is often misdiagnosed. It is occasionally confused with the more prevalent motor neurone disease, a degenerative neurological disorder marked by the degeneration of neurons in the brain and spinal cord.
Among the tests that can be done to determine whether someone has Kennedy's disease is a blood test to look for elevated serum creatine kinase (CPK) levels. Kennedy's disease patients typically have higher levels of this enzyme circulating in their blood than normal.
Even if a person is asymptomatic or a carrier, genetic tests utilising blood samples can determine whether the Kennedy's disease gene is present.
Complications
Kennedy disease patients generally have a normal life expectancy. Falls, aspiration pneumonia and respiratory failure are examples of Kennedy disease complications that could be seriously harmful.
Falls are a potentially catastrophic side effect of mobility loss and muscular wasting. The danger of falls can be minimised with the aid of assistive devices such as wheelchairs, a cane and a walker, and with physiotherapy and occupational therapy.
People with Kennedy's disease may lose weight, become dehydrated and lose energy as a result of their increased swallowing problems.
The two most dangerous complications are aspiration pneumonia and respiratory failure. However, only a small percentage of Kennedy disease patients suffer from these
Treatment
There is currently no cure for Kennedy's disease. Treatment consists of supportive and symptomatic care.
To reduce muscle deterioration and atrophy and help adapt to the progressive disease and maintain physical skills, physiotherapy and occupational therapy may be beneficial.
The goal of physiotherapy is to assist in managing the existing symptoms and help preserve functional independence for as long as feasible.
Occupational therapists are able to provide aids to assist with walking and modifying daily living tasks. It may be necessary to learn safe and healthy swallowing techniques.
Speech therapy may assist those whose speech the disease adversely affects.
Breast reduction surgery may sometimes be done for those with gynecomastia.
Androgens contribute to the progression of Kennedy's disease. It is possible to inhibit androgen activity surgically. The possible adverse side effects of androgen suppression, however, include altered mental states, osteoporosis and decreased muscle strength.
Research is being conducted into the possibility of short-term androgen reduction therapy.
Medication may be prescribed to treat specific symptoms of Kennedy's disease.
The information in this article is provided as a public service by the Cimas iGo Wellness programme, which is designed to promote good health. It is provided for general information only and should not be construed as medical advice. Readers should consult their doctor or clinic on any matter related to their health or the treatment of any health problem. — [email protected] or WhatsApp 0772 161 829 or phone 024-2773 0663
