Charcot-Marie-Tooth disease

Also known as: Hereditary Motor and Sensory Neuropathy; Peroneal Muscular Atrophy

Background

Charcot-Marie-Tooth disease (CMT) is a genetic disorder characterised by slowly progressive muscular weakness. The onset of the condition may be from childhood to late middle or old age, but most frequently is first apparent in childhood.

Credits

Medical text written November 1991 by Contact a Family. Approved November 1991 by Professor M Patton, Professor of Medical Genetics, St Georges Hospital Medical School, London, UK and Dr J E Wraith, Consultant Paediatrician, Royal Manchester Children’s Hospital, Manchester, UK. Last updated September 2010 by Dr David Hilton-Jones, Clinical Director, Muscle and Nerve Centre, Radcliffe Infirmary, Oxford, UK.

What are the symptoms?

Onset is in the lower limbs first, causing weakness around the ankles and, often, an abnormality in the shape of the feet (high in-step, which doctors call ‘pes cavus’). After many years, weakness may develop in the hands and spread upwards in the lower limbs to affect the knees and thighs. Mild loss of sensation may be present in the feet and hands.

What are the causes?

The underlying cause is an abnormality (called a mutation) in one of the genes responsible for producing a protein that is essential for normal nerve function. Each nerve is made up of many thousands of proteins. CMT can be caused by mutations in any one of about 30 genes – although each protein that is affected is different the end result is a similar in terms of the overall symptoms experienced by an individual with CMT.

How is it diagnosed?

The most common form (called type 1A), which accounts for about 70 per cent of all CMT patients, affects a protein called PMP22 and can be diagnosed by a blood test looking at the gene responsible for producing that protein. But for other forms it is more complicated. The basic diagnosis of CMT can be made by electrical tests known as ‘nerve conduction studies’.

To define the specific genetic abnormality responsible for CMT requires blood tests to look at the DNA, but at present that is only available for a small number of the responsible genes.

Whilst there are advantages in knowing the precise cause (mainly for advising other family members about risks of developing the condition) the lack of such knowledge does not affect the basic management of the condition.

How is it treated?

At present there is no specific drug or genetic treatment. But much can be done to help and support the individual – important members of the care team include physiotherapists, occupational therapists and orthotists (who make splints and other aids).

Inheritance patterns and prenatal diagnosis

Inheritance patterns
Three patterns of inheritance are noted. Autosomal dominant is the most common pattern of inheritance. Autosomal recessive inheritance is the least common. X-linked inheritance has been noted where the condition may be passed to both sons and daughters – affected sons will usually display more severe symptoms.

Prenatal diagnosis
In families who have type 1a prenatal diagnosis is now becoming available but is rarely requested.

Is there support?

Charcot-Marie-Tooth UK

Freephone helpline: 0300 323 6316
Email: enquiries@cmt.org.uk
Website: cmt.org.uk

The Organisation is a Registered Charity in England and Wales No. 1112370. It offers information and support to people with Charcot-Marie-Tooth Disease (also known as Hereditary Motor and Sensory Neuropathy or Peroneal Muscular Atrophy), and their families and carers. The Organisation produces publications, and has a network of local groups, a Members Forum and a youth section on its website.

Group details last updated April 2018.

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