Facio Scapulo Humeral MD Explained
What is it?
It is a muscle wasting condition, caused by a genetic fault, which may be affecting the regulation of the level of many of the different proteins in muscles.
Why this name, and are there others?
The name describes the usual distribution of weakened muscles: ‘facio'=facial; ‘scapulo'=shoulder blade; ‘humeral'= upper arm. Landouzy-Dejerine and facioscapuloperoneal muscular dystrophy are two previously used terms. Also, some people with a diagnosis of scapulohumeral or scapuloperoneal syndromes may have this condition. However, the legs can also be affected.
How rare is it?
It is probably the third most common muscular dystrophy (after Duchenne and myotonic dystrophies), although its frequency may vary in different places and quite possibly in different racial groups. Estimates of frequency have varied from one in about 400,000 to one in 20,000. In Britain, the frequency is at least one person in every 50,000, and probably closer to one in 20,000, accounting for between about 1200 and 3000 cases in all.
What causes it?
It is a genetic condition, present from when or soon after egg and sperm come together at conception. Normally, at a particular site on the gene map, each of us has many copies of a particular sequence of genetic instruction (DNA), arranged like a train of identical carriages. FSHD is caused when the number of copies is reduced below a certain level, like a train having too few carriages. In some way this seems to influence the production or assembly of several of the protein components of the affected muscles.
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