What causes EDMD?
Most EDMD cases are caused by mutations in the EMD, FHL1, or LMNA gene. The EMD and LMNA genes provide instructions to build proteins that are part of the nuclear envelope within a muscle cell. The nucleus is the place where genetic information is stored, and defects in the nuclear envelope can cause problems with muscle function. The FHL1 gene exists in different isoforms and is vital for muscle function.
The EMD and FHL1 genes are located on the X chromosome. Because women have two X chromosomes, the condition only manifests if both copies of a gene located on the X chromosome is mutated. Men, however, have only one X chromosome, and a mutation in the only copy of an X chromosome-localized gene can cause EDMD. Therefore, men are much more frequently affected by X-linked EDMD than women.
The LMNA gene is located on a sex-unrelated chromosome, a so-called autosome. Mutations in this gene affect women and men equally. They can be inherited in an autosomal recessive or dominant manner. An autosomal dominant condition occurs when an individual inherits one copy of a faulty gene. In an autosomal recessive condition, both gene copies are mutated.
What are the symptoms of EDMD?
EDMD symptoms are related to contractures, and weakness of skeletal and heart muscles.
Contractures (shortening of tendons) restrict movement of the joints, especially in the elbows and ankles.
Most patients also experience muscle weakness and wasting that mainly affects the upper arms and lower legs but also shoulders, neck, and hips.
Because EDMD also affects the heart muscles, patients can develop heart abnormalities. Typical symptoms include palpitations (strong, irregular heartbeat), fatigue, poor exercise tolerance, and arrhythmias (irregular heartbeat).
How is EDMD diagnosed?
The diagnosis of EDMD is based on a detailed clinical evaluation, which includes the patient’s and family’s medical history, and assessment of the symptoms. Electromyography is used to test muscle function. Certain markers in the blood, such as creatine kinase (CK), are an indicator of muscle damage.
How is EDMD treated?
Mobility devices, such as canes, wheelchairs, and braces, can improve mobility.
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