Types of FSHD

Facioscapulohumeral muscular dystrophy or FSHD is the most prevalent of the nine primary types of muscular dystrophy affecting adults and children. Muscular dystrophy in general connotes a genetic, hereditary muscle disease that causes progressive muscle weakness. FSHD is also broadly characterized as a neuromuscular disease (NMD), as muscular dystrophy is a subset of NMD. Muscular dystrophies are alike in that they cause progressive skeletal muscle weakness, defects in the biochemical, physical and structural components of muscle, and the death of muscle cells and tissue. However, researchers believe that the causes of each of the muscular dystrophies are not necessarily the same.

The major symptom of FSHD is the progressive weakening and loss of skeletal muscles. The usual location of these weaknesses at onset is the origin of the name: face (facio), shoulder girdle (scapulo) and upper arms (humeral). Early weaknesses of the muscles of the eye (open and close) and mouth (smile, pucker, whistle) are distinctive for FSHD. These symptoms, in combination with weaknesses in the muscles that stabilize the scapulae (shoulder blades), are often the basis of the physician’s diagnosis of FSHD.

In most cases, FSHD muscle involvement starts in the face and slowly progresses to the shoulder and upper arm muscles and then down to the abdominal and foot extensor muscles. Foot drop and foot weakness are early manifestations. Initial signs of FSHD include difficulty reaching above the shoulder level, foot drop, scapular winging and facial weakness. Weakness in the abdominal muscles can cause a protuberant abdomen and lumbar lordosis. The lower abdominal muscles are usually weaker than the upper abdominal muscles. This distribution of weakness is not seen in many other diseases and, therefore, is very specific to FSHD.

Although the progression of FSHD is quite variable, it is usually relatively slow. With FSHD, most affected people develop unbalanced (side-to-side) weaknesses. The reason for this asymmetry is unknown.

In more than half of FSHD cases, there are other symptoms including high-frequency hearing loss and/or abnormalities of blood vessels in the back of the eye. The vascular abnormalities in the back of the eye lead to vision problems in only about 1% of the cases. Since these abnormalities are not exclusive to FSHD, one must bear in mind that their presence alone, in an FSHD at-risk individual, is insufficient for a diagnosis of FSHD.

Although not typical, some patients with FSHD have respiratory insufficiency, especially those with severe FSHD…