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DECEMBER 2022 InTouch | 7 Facioscapulohumeral dystrophy (FSHD), is the third most common muscular dystrophy after Duchenne muscular dystrophy and myotonic dystrophy. FSHD affects around 1 in 15,000 to 1 in 20,000 people worldwide. The term “facioscapulohumeral” uses three Latin roots to describe the location of muscles characteristically involved in the disease: facio (face), scapulo (shoulder blade), and humeral (upper arm). Muscles of the abdomen, hips, and lower legs can also be involved. Genetics and pathophysiology FSHD is an autosomal dominant disorder in 95% of cases, with de novo (i.e., spontaneous) mutations accounting for up to a third of these. This means an individual with FSHD1 has a 50% chance of passing the gene down to his or her offspring. Inheritance in the remaining 5% of cases is more complex and is referred to as FSHD2. FSHD1 and FSHD2 are clinically indistinguishable from one another and are differentiated only by the underlying genetic variance. In both FSHD1 and FSHD2, the downstream result of the gene variant is ultimately the same: the inappropriate production of a protein called DUX4 which is toxic to skeletal muscle. Features of FSHD The onset of symptoms in FSHD varies from infancy to late adulthood, with most people noticing weakness beginning in their late teens to early 20s. The most common initial Facioscapulohumeral muscular dystrophy (FSHD) YOUR CONDITION IN REVIEW symptoms are related to weakness of the periscapular muscles (shoulder blade stabilizers) resulting in difficulty lifting objects overhead. Facial weakness also begins early in the course of the disease, but is often unnoticed or disregarded. Typical symptoms might include the inability to whistle or drink through a straw, or sleeping with the eyes slightly open. Less commonly a person with FSHD may notice leg weakness as their initial symptom, but shoulder and facial weakness are also likely to be evident when examined by one who is familiar with muscular dystrophies. Asymmetric weakness is common in FSHD and is another hallmark that distinguishes it from other muscular dystrophies. The following signs and symptoms may be present: • Facial weakness resulting in difficulties whistling, puckering, smiling, or closing the eyes. • Weakness around the shoulder blades preventing movements such as throwing objects and raising the arms. • Winging of the shoulder blade due to reduced strength of the stabilizing muscles. • Atrophy of the triceps and biceps muscles, while the deltoid and forearm muscles remain relatively unaffected. • Abdominal muscle weakness resulting in a protuberant abdomen and causing difficulty sitting up from a supine position. • Excessive curvature of the lower spine (lordosis) due to paraspinal muscle weakness. • Weakness in the muscles surrounding the hip and those of the upper leg, causing problems Continued over ...