Emery-Dreifuss muscular dystrophy

Infobox_Disease
Name = PAGENAME


Caption =
DiseasesDB = 31705
DiseasesDB_mult = DiseasesDB2|33543 DiseasesDB2|31704 | ICD10 = ICD10|G|71|0|g|70
ICD9 = ICD9|359.0-ICD9|359.1
ICDO =
OMIM = 181350
OMIM_mult = OMIM2|604929 OMIM2|310300 | MedlinePlus =
eMedicineSubj = neuro
eMedicineTopic = 513
MeshID = D020389

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

It is named after Alan Emery and Fritz E. Dreifuss [WhoNamedIt|synd|1564] cite journal |author=Emery AE, Dreifuss FE |title=Unusual type of benign x-linked muscular dystrophy |journal=J. Neurol. Neurosurg. Psychiatr. |volume=29 |issue=4 |pages=338–42 |year=1966 |pmid=5969090 |doi=] cite journal |author=Emery AE |title=Emery-Dreifuss syndrome |journal=J. Med. Genet. |volume=26 |issue=10 |pages=637–41 |year=1989 |pmid=2685312 |doi=]

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 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.

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.

* 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, 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.

* 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.

ee also

* Laminopathies
* Noncompaction Cardiomyopathy

References

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