Kennedy's disease (spinal and bulbar muscular atrophy): symptoms, diagnosis and care

Kennedy's disease is a form of motor neurone disease that is inherited and slowly progressive. Kennedy's Disease UK describes it as characterised by the degeneration of lower motor neurones within the spinal cord and brainstem, which causes progressive weakening and wasting of the muscles, particularly in the arms and legs. The bulbar muscles of the face, mouth and throat are also affected, which is where the name spinal and bulbar muscular atrophy comes from.

It is not the same as the more common amyotrophic lateral sclerosis, although the two can look similar at first. The NHS describes motor neurone disease as causing muscle weakness that gets worse over a few months or years and is usually life-shortening, whereas people with Kennedy's disease typically progress much more slowly. The charity notes that people with Kennedy's disease are supported by the MND Association even though it is not classed as a type of MND.

Because it is caused by a change in a hormone receptor, the disease can also affect hormonal and metabolic function. The charity lists low sperm count, reduced sex drive, enlarged breast tissue (gynaecomastia) and shrunken testicles among the features.

The condition is caused by a mutation in the androgen receptor gene on the X chromosome. Kennedy's Disease UK explains that, because the disease is recessive, women who carry the altered gene have another normal copy and generally do not develop the disease, although in rare cases they can have mild symptoms. Each son of a carrier mother has a 50 per cent chance of inheriting the gene and developing the disease. The charity also says daughters of men with Kennedy's disease are carriers, while sons of affected men do not inherit the altered gene.

A UK research study summary describes the condition as caused by an expansion in the androgen receptor gene and says it only affects males, with women being carriers. A charity information page for clinicians reports that a UCL study estimated the prevalence at about 1 in 6,888 males, 4.4 times higher than previously reported, which suggests it is under-recognised.

Genetic counselling is recommended for families. The charity says it can be requested through a GP or accessed privately, that it normally comes before genetic testing, and that options for people planning a family include prenatal or preimplantation diagnosis, depending on personal choice.

Kennedy's Disease UK lists swallowing difficulties, speech difficulties, hand tremors, absent reflexes, and muscle weakness, wastage, twitches, cramps and spasms, alongside the hormonal features above. In its carriers information it says early signs include tremor of the hands, muscle cramps with exertion, and fleeting muscle twitches, followed by limb weakness often beginning around the pelvis or shoulders, and then weakness of the face and tongue that can cause difficulty swallowing and speaking.

The charity gives a typical age at which symptoms start as the 30s to 50s. It also lists non-insulin-dependent diabetes mellitus and infertility among possible associated problems. Women who are carriers usually have no symptoms or very mild ones, usually muscle cramps and fatigue.

Progression is gradual over many years. A UK research summary describes slowly progressive weakness that often leads to wheelchair dependence, together with impairment of speech and swallowing and multiple hormonal effects, which is why monitoring matters.

The charity says your GP can refer you to a neurologist, who can take a definitive blood test to establish whether you have the genetic defect, and can judge the likelihood of Kennedy's disease from a physical examination. Its information for doctors describes the gold standard as molecular genetic testing identifying an expansion of a CAG repeat in the androgen receptor gene. Blood tests may show a raised creatine kinase, a muscle enzyme.

This matters because of misdiagnosis. The charity's information for doctors lists recorded misdiagnoses including amyotrophic lateral sclerosis, spinal muscular atrophy, Guillain-Barre syndrome, myasthenia gravis, multiple sclerosis and Parkinson's disease, and notes that when there is no known family history it can take many years for a definitive diagnosis. For comparison, the NHS says tests used to help diagnose MND include blood tests, nerve function tests and an MRI scan to rule out other conditions.

If you are a man in his 30s or later with weakness, cramps, tremor or swallowing and speech changes, and a maternal male relative with similar problems, mention the family history to your doctor.

There is no cure and no treatment that stops progression at present, according to the charity and the UK research summary. Management is supportive and coordinated by a neurologist with other professionals. Kennedy's Disease UK lists medicines to reduce muscle cramps and tremors, plenty of rest and avoidance of exhaustion, a healthy balanced diet, gentle regular aerobic exercise, regular stretching to reduce cramping, pain management, and support from speech, occupational and physiotherapy.

Speech and language therapy assesses swallowing and communication, and dietitians help if swallowing is affected. Physiotherapy and occupational therapy help with mobility, equipment and home adaptations. Because the condition is hormone related, an endocrinologist may be involved for diabetes or other hormonal issues, and the person's diabetes risk should be checked.

The charity says trials of new treatments are underway. A UK natural history study based at a national neurology hospital, whose summary notes a dedicated Kennedy's disease NHS clinic there, is collecting information to prepare for clinical trials.

See a GP promptly about new or worsening weakness, difficulty swallowing or speaking, repeated chest infections or breathlessness. Call 999 or go to A&E for severe difficulty breathing, choking that does not clear, or sudden severe weakness. Tell any emergency team that you have Kennedy's disease and carry written information about your condition. The charity links to specialist advice on anaesthesia for people with the condition.

The charity provides a document for emergency rooms and clinicians, which many people keep with them.

Kennedy's Disease UK is a patient-led charity that provides information, a community and updates on research. The MND Association supports people living with Kennedy's disease as well as those with MND, according to the charity. Carers and carriers have their own information too.

Care is available through the NHS. Your GP can refer you to a neurologist and, where needed, to rehabilitation, speech and swallowing, and genetic services. Some people seek private neurology opinions to speed up diagnosis, which is reasonable, but because genetic testing and long-term multidisciplinary care are needed, it is worth ensuring that the results are shared with your NHS team.