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Congenital Muscular Dystrophy

Background

The congenital muscular dystrophies (CMDs) are a group of inherited muscle disorders that typically become apparent at birth or in early infancy and are characterised by floppiness, weak muscles or problems with the mobility of joints.

Credits

Medical text written September 2011 by Dr M Scoto Clinical Research Associate, and Dr A Manzur, Consultant Paediatric Neurologist, Dubowitz Neuromuscular Centre, UCL Institute of Child Health and Great Ormond Street Hospital, London, UK.

What are the symptoms?

Symptoms in small babies include hypotonia (floppiness) and low muscle tone. As the muscles are weak and immobile, contractures (tightness) in the hip, ankle, knee and elbow joints are common. In children that do not have contractures, initial problems may be difficulties holding the head, and delays in sitting and walking.

Some forms of CMDs can have associated brain changes on a magnetic resonance imaging (MRI) scan. The pattern of these brain MRI changes helps to identify the subtype of CMD. Some, but not all children with CMD and brain changes visible on an MRI scan, may have learning difficulties (see entry Learning Disability) with or without epileptic seizures (see entry Epilepsy). Learning difficulties can be mild, moderate or severe and do not get worse over time.

What are the causes?

Approximately 40 per cent of children with CMD have a mutation in the LAMA2 gene, which is responsible for producing the protein merosin. At least 13 causative genes have been implicated in CMD, each of them resulting in specific symptoms for a patient. A number of people with CMD don't have mutations in any of the genes already described.

How is it diagnosed?

A high level of the enzyme creatine kinase (CK) can indicate the condition. Electromyography (measuring the electrical activity of muscle) may be undertaken to establish how well the muscles are working, but is not essential. Muscle imaging, usually with ultrasound, and muscle biopsy are used to identify the exact type of CMD. MRI scans of the brain can help to diagnose particular subtypes of CMD that cause changes in the brain. In types of CMD where the genetic defect is known, genetic testing offers a definitive diagnosis.

How is it treated?

There is no cure for CMD. A programme of physiotherapy and exercises should be devised soon after diagnosis to improve muscle function and mobility. If there are problems with breathing at night, an overnight breathing study maybe needed to monitor breathing quality and a ventilator may be used to assist breathing. Flu jabs and other vaccinations are advisable in some children to prevent the occurrence of chest infections.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
CMDs are transmitted in an autosomal recessive manner in most instances, although sporadic cases have been documented.

Prenatal diagnosis
This is possible via amniocentesis after 15 weeks of pregnancy or chorionic villus sampling between 10 and 13 weeks of pregnancy if the genetic defect causing the subtype of CMD in a family is known.

Is there support?

Muscular Dystrophy UK

Helpline: 0800 652 6352
Email: info@musculardystrophyuk.org
www.musculardystrophyuk.org

The Charity is a Registered Charity in England and Wales No. 205395, and Scotland No. SC039445. It provides information and support for anyone affected by muscular dystrophy and other muscle-wasting conditions. Muscular Dystrophy UK also provide grants towards the cost of specialist equipment.

Group details last updated September 2017.

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