Emery-Dreifuss muscular dystrophy

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Emery–Dreifuss muscular dystrophy

ICD-10	G710
ICD-9	359.0-359.1
OMIM	181350 604929 310300
DiseasesDB	31705 33543 31704
MedlinePlus	[1]
eMedicine	{{{eMedicineSubj}}}/513
MeSH	{{{MeshNumber}}}

Emery–Dreifuss muscular dystrophy is a form of muscular dystrophy that chiefly affects muscles used for movement (skeletal muscles) and heart (cardiac) muscle.

It is named after Alan Eglin H. Emery (1928–) and Fritz E. Dreifuss.

Presentation

Among the earliest features of this disorder are joint deformities called contractures, which restrict the movement of certain joints. Contractures become noticeable in early childhood to teenage years and most often involve the elbows, ankles, and neck. Most affected individuals also experience slowly progressive muscle weakness and wasting, beginning in muscles of the upper arms and lower legs and progressing to muscles in the shoulders and hips. A power chair or scooter or wheelchair may be needed by adulthood.

Almost all people with Emery–Dreifuss muscular dystrophy have heart problems by adulthood. In many cases, these heart problems stem from abnormalities of the electrical signals that control the heartbeat (cardiac conduction defects) and abnormal heart rhythms (arrhythmias). If untreated, these abnormalities can lead to an unusually slow heartbeat (bradycardia), fainting (syncope), and an increased risk of stroke and sudden death.

Classification

The types of Emery–Dreifuss muscular dystrophy are distinguished by their pattern of inheritance: X-linked, autosomal dominant, and autosomal recessive.

• Although the three types have similar signs and symptoms, researchers believe that the features of autosomal dominant Emery–Dreifuss muscular dystrophy are more variable than the other types. A small percentage of people with the autosomal dominant form experience heart problems without any weakness or wasting of skeletal muscles.
• X-linked Emery–Dreifuss muscular dystrophy is the most common form of this condition, affecting an estimated 1 in 100,000 people.
• The autosomal recessive type of this disorder appears to be very rare; only a few cases have been reported worldwide. The incidence of the autosomal dominant form is unknown.

Genetics

Mutations in the EMD and LMNA genes cause Emery–Dreifuss muscular dystrophy. The EMD and LMNA genes provide instructions for making proteins that are components of the nuclear envelope, which surrounds the nucleus in cells. The nuclear envelope regulates the movement of molecules into and out of the nucleus, and researchers believe it may play a role in regulating the activity of certain genes.

Type	OMIM	Gene	Description
EDMD1	310300	EMD	Most cases of Emery–Dreifuss muscular dystrophy are caused by mutations in the EMD gene. This gene provides instructions for making a protein called emerin, a transmembrane protein of the inner nuclear membrane which appears to be essential for the normal function of skeletal and cardiac muscle. Most EMD mutations prevent the production of any functional emerin. It remains unclear how a lack of this protein results in the signs and symptoms of Emery-Dreifuss muscular dystrophy.
EDMD2, EDMD3	181350	LMNA	Less commonly, Emery–Dreifuss muscular dystrophy results from mutations in the LMNA gene. This gene provides instructions for making two very similar proteins, lamin A and lamin C. Most of the LMNA mutations that cause this condition result in the production of an altered version of these proteins.
EDMD4	612998	SYNE1
EDMD5	612999	SYNE2
EDMD6	300696	FHL1

See also

• Laminopathies
• Noncompaction Cardiomyopathy

External links

• Overview of condition at NLM Genetics Home Reference

• GeneReviews/NCBI/NIH/UW entry on Emery–Dreifuss muscular dystrophy
• GeneReviews/NCBI/NIH/UW entry on SYNE1-Related Autosomal Recessive Cerebellar Ataxia

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