Emery-Dreifuss muscular dystrophy
Encyclopedia
Emery–Dreifuss muscular dystrophy is a condition that chiefly affects muscle
s used for movement (skeletal muscles) and heart (cardiac) muscle.
It is named after Alan Eglin H. Emery (1928–) and Fritz E. Dreifuss
.
s, 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.
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.
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s used for movement (skeletal muscles) and heart (cardiac) muscle.
It is named after Alan Eglin H. Emery (1928–) and Fritz E. Dreifuss
Fritz E. Dreifuss
Fritz E. Dreifuss, MD was a German-born, American neurologist and subspecialist in epilepsy based at the University of Virginia in Charlottesville, Virginia, USA.- Early life :He was born in Dresden, Germany...
.
Presentation
Among the earliest features of this disorder are joint deformities called contractureContracture
A muscle contracture is a permanent shortening of a muscle or joint.. It is usually in response to prolonged hypertonic spasticity in a concentrated muscle area, such as is seen in the tightest muscles of people with conditions like spastic cerebral palsy....
s, 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
Bradycardia
Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
), fainting (syncope
Syncope (medicine)
Syncope , the medical term for fainting, is precisely defined as a transient loss of consciousness and postural tone characterized by rapid onset, short duration, and spontaneous recovery due to global cerebral hypoperfusion that most often results from hypotension.Many forms of syncope are...
), and an increased risk of stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
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 LMNALMNA
Lamin A/C also known as LMNA is a protein that in humans is encoded by the LMNA gene. Lamin A/C belongs to the lamin family of proteins.-Function:...
genes cause Emery–Dreifuss muscular dystrophy. The EMD and LMNA genes provide instructions for making proteins that are components of the nuclear envelope
Nuclear envelope
A nuclear envelope is a double lipid bilayer that encloses the genetic material in eukaryotic cells. The nuclear envelope also serves as the physical barrier, separating the contents of the nucleus from the cytosol...
, which surrounds the nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
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 | EMD Emerin Emerin, together with MAN1, is a LEM domain-containing integral membrane protein of the nuclear membrane in vertebrates. The function of MAN1 is not extensively known, but emerin is known to interact with nuclear lamins, barrier-to-autointegration factor , nesprin-1α, and a transcription... |
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. | |
| EDMD2, EDMD3 | LMNA LMNA Lamin A/C also known as LMNA is a protein that in humans is encoded by the LMNA gene. Lamin A/C belongs to the lamin family of proteins.-Function:... |
Less commonly, Emery–Dreifuss muscular dystrophy results from mutations in the LMNA gene. This gene provides instructions for making two very similar proteins, lamin Lamin Nuclear lamins, also known as Class V intermediate filaments, are fibrous proteins providing structural function and transcriptional regulation in the cell nucleus. Nuclear lamins interact with membrane-associated proteins to form the nuclear lamina on the interior of the nuclear envelope... 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 | SYNE1 SYNE1 SYNE1 is a gene.-External links:*... |
||
| EDMD5 | SYNE2 SYNE2 Nesprin-2 is a protein that in humans is encoded by the SYNE2 gene.-Further reading:... |
||
| EDMD6 | FHL1 FHL1 Four and a half LIM domains protein 1 is a protein that in humans is encoded by the FHL1 gene.-Role in muscle disorders:FHL1 has been shown to be heavily expressed in skeletal and cardiac muscles... |