Facioscapulohumeral muscular dystrophy (FSHD) is the third most common type of muscular dystrophy worldwide. The prevalence of the disease is estimated at about one in 20,000.
The name of the disease relates to the areas of the body that are most affected early on in the disease: the face (facio), the shoulder blade (scapula) and the upper arm (humeral). As the disease progresses it can also affect the legs. FSHD has also been known by the name Landouzy-Dejerine (after two people who first characterised the disease). The disease symptoms often present in the teenage years when a person experiences difficulty in raising one or both arms, notices prominent shoulder blades or wasting of upper arm muscles. Weakness around the mouth may make it hard to pucker, whistle or smile. Weakness around the eyes may result in eyes not closing properly at night and an inability to scrunch the eyes so that the lashes disappear. The symptoms increase in severity over time. It can be a painful and debilitating disease leading to the loss of ambulation; however, in the mildest cases people can remain unaware of the symptoms even into late adulthood. FSHD does not typically reduce the lifespan of the affected person and people diagnosed with FSH can still live into their 90s.
Symptoms can present much earlier in life in what is described as infantile FSHD. This conditions often a much more severe form of the disease. In addition to muscle weakness, children with infantile FSHD can have hearing loss as well abnormalities of the blood vessels of their retina. Progressive weakness of the legs can start to develop by the teenage years and lead to the need for a wheelchair.