Facioscapulohumeral muscular dystrophy (FSHD) is a disease that gradually causes muscles to deteriorate. Muscular dystrophies in general are hereditary muscle diseases that cause progressive muscle weakness. FSHD predominantly affects the upper body, unlike Duchenne muscular dystrophy and Becker muscular dystrophy, which affect the lower body. Doctors Landouzy and Dejerine first described FSHD in 1885 and, as a result, the disease is sometimes called Landouzy-Dejerine muscular dystrophy.
The major symptom of FSHD is the gradual weakening and loss of skeletal muscles. The usual location of these weaknesses give the disease its name: face (facio), shoulder girdle (scapulo), and upper arms (humeral). There is wide variability in the age at which symptoms first appear and the severity of the disease, which varies even within affected members of the same family.
FSHD is caused by a genetic defect or mutation in a person's DNA (deoxyribonucleic acid). DNA is packaged on larger structures called chromosomes. Humans have 23 pairs of chromosomes, including 22 pairs of autosomes and one pair of sex chromosomes. Almost all cases of FSHD are associated with a deletion, or a piece of missing DNA, from chromosome 4. This region of deleted DNA does not belong to any known genes, but is believed to be involved in the regulation of other genes.
FSHD has been classified into three types: FSHD type 1A (chromosome 4-linked FSHD), FSHD type 1B (non-chromosome 4-linked FSHD), and infantile FSHD (IFSHD). The symptoms are the same for all types. The difference between the types depends on the type of mutation that causes the disease. More than 98% of cases are of the FSHD type 1A.
Because FSHD is inherited, the only known risk factor is a family history of the disorder. It affects men and women equally. FSHD is distributed worldwide and does not occur to a greater degree in any racial or ethnic group or geographic location.
Although there is currently no known cure for FSHD, many treatments are available to improve symptoms and maximize the quality of life. With proper treatment, many individuals with FSHD have normal life expectancies.
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types of the disease
General: Facioscapulohumeral muscular dystrophy (FSHD) has been classified into three types: FSHD1A, FSHD1B, and IFSHD. The symptoms are the same for each type.
FSHD1A: The most common form of FSHD is FSHD type 1A, or chromosome 4-linked FSHD. FSHD1A can be detected by genetic testing for missing or deleted DNA from a region of chromosome 4 called D4Z4. Patients missing the most DNA from this region typically have the most severe symptoms, such as an inability to walk.
FSHD1B: FSHD type 1B, or non-chromosome 4-linked FSHD, is much less common than FSHD1A. Researchers are not sure whether it is caused by mutations in the genes that cause FSHD1A or in other genes.
IFSHD: Infantile FSHD (IFSHD) is rare. It is a more severe form of FSHD1A or FSHD1B, in which symptoms occur in early childhood. What makes the disease more severe has not yet been determined. Hearing loss, vision problems, and seizures are associated with IFSHD.