Scientists supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases have found that people with facioscapulohumeral muscular dystrophy (FSHD) have an exclusive association with one of the two different forms, or alleles, of the chromosomal region linked to the disease.

Silvèere van der Maarel, Ph.D., and his colleagues at Leiden University Medical Center and University Medical Center Nijmegen in The Netherlands examined the alleles 4qA and 4qB in 80 control individuals and 80 individuals with FSHD. The alleles occurred with roughly equal frequency in the control group, but in the FSHD group, the affected allele was always of the 4qA type. Their work may lead to a better understanding of the instability of FSHD's genetic locus.

FSHD, the third most common genetic disease of skeletal muscle, affects approximately one in 20,000 persons. Symptoms may begin during infancy, late childhood or early adulthood. The first sign is usually facial weakness, with difficulty smiling, whistling and closing the eyes. Later, there is difficulty raising the arms or flexing the wrists and ankles. The disease occurs in both sexes and in all racial groups.

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Lemmers R, de Kievit P, Sandkuijl L, Padberg G, van Ommen G, Frants R, van der Maarel S. Facioscapulohumeral muscular dystrophy (FSHD) is uniquely associated with one of two variants of the 4q subtelomere. Nature Genetics 2002;32(2):235-236.