What is muscular dystrophy?
There are a number of different types of muscular dystrophy. They are muscle diseases which have 3 features in common: they are hereditary, they are progressive, and each causes a characteristic, selective pattern of muscle weakness.
Which muscle groups are most affected in facioscapulohumeral (FSH) dystrophy?
The name facioscapulohumeral gives an indication of the distribution of muscle weakness, but not a complete one. ‘Facio’ refers to the face, ‘scapulo’ to the scapula or shoulder blade, ‘humeral’ to the upper arm between shoulder and elbow.
The facial muscles are affected. The selective pattern of weakness often produces a recognisable facial appearance more noticeable when the muscles are in use, as in speaking or in producing facial expression. Weakness of eye closure may cause the affected person to sleep with the eyes slightly open. The face tends to become less than usually lined with age.
Muscles about the shoulder blades are affected. This leads to ‘winging of the scapulae’, especially when the arms are held forward horizontally. ‘Winging’ of the shoulder blades is a backward protrusion of their inner edges when the arms are held forward horizontally. The bulk of the muscles between the shoulder blades may be reduced.
The muscles which rotate the scapulae are affected. Looked at from behind, a normal person can be seen to raise the arms sideways to about horizontal with little or no change in the position of the scapulae but to raise the arms above the head requires rotation of the scapulae. FSH dystrophy of more than very mild severity usually makes rotation of the scapulae, and therefore raising of the arms, difficult or impossible.
The muscles around the humerus or upper arm bone are affected, causing weakness of bending (flexion) and straightening (extension) of the elbow. The forearm muscles are usually better developed than the upper arm muscles so that the strength of wrist and finger movements is relatively normal. A feature of the weakness in FSH is that it is typically asymmetrical. Nearly always, in an affected person, some muscle groups are stronger on the left and others stronger on the right. The other muscular dystrophies tend to be symmetrical in their effects.
Are other muscles affected? Are the legs or back ever affected?
The name ‘facioscapulohumeral’ gives an incomplete idea of the extent of weakness. In people who are more than slightly affected, there is nearly always some weakness of the back and the lower limbs. In some people it is moderately severe and occasionally it is very severe.
How may the lower limbs be affected?
As with all muscular dystrophies, weakness is selective. Usually the calf muscles are strong and toe-walking is easy. Conversely the muscles in front of the lower leg are weak causing foot-drop, a tendency to trip and inability to walk on the heels with toes raised.
The big muscles which move the hips and knees may also be affected. Selective weakness may again be conspicuous, some patients having very weak ability to extend (straighten) the hip joints but very strong ability to straighten the knees.
How is the back affected?
The most noticeable effect is on posture. Not everyone with FSH has altered posture, but many do. The main effect is an exaggeration of the normal forward curvature of the spine above the pelvis. This exaggerated curve is called lordosis. Occasionally it is very conspicuous and in that case the abdomen is excessively protuberant while the shoulders are held back excessively.
What difficulties are usually caused by FSH?
There is often difficulty raising the hands above shoulder level causing problems with combing the hair, reaching high shelves or hanging out clothes to dry. Lifting heavy objects may be difficult, even below shoulder level. Some people first notice a problem in sport or recreation, as in swimming overarm or serving at tennis. The effects on the lower limbs may cause foot-drop and a tendency to trip, an awkward gait with lordosis, a tendency for one or both knees to give way and difficulty with stairs and steps.
Because weakness is asymmetrical, often the initial complaint is about trouble with one shoulder only, or one leg.
Are people with FSH all affected to about the same extent?
Severity varies greatly, even between affected members of one family. ‘Average severity’ means becoming aware of disability in adolescence or early adulthood, being mildly to moderately handicapped through early and middle adult life, somewhat more severe in late middle age, retaining the ability to walk and having a normal lifespan.
At one end of the spectrum of severity, affected people are handicapped in infancy or early childhood and are unable to walk by adolescence or early adulthood. At the other end of the spectrum, an affected person might never experience any handicap at all and even an experienced physician would find it difficult to be sure that he or she was affected.
The heart is a muscle. Is the heart affected?
The heart is not affected in FSH dystrophy.
Are other tissues or organs affected?
Recent research has shown changes in the eyes of people with FSH dystrophy. Changes in the blood vessels at the back of the eye have been reported and researchers have questioned whether there might be similar changes in the blood vessels in the muscles. These changes seldom cause trouble with vision, nevertheless it has been suggested that people with FSH dystrophy should have periodic examination by an eye specialist.
In children who are affected by severe FSH dystrophy of early onset, deafness is frequent. Since this was first observed, deafness has been looked for in more mildly affected people and it has been found that it is more frequent than in the general population.
Is FSH dystrophy always progressive?
In very mild cases, it may not be possible to detect progression of weakness. In the average case, progression is evident but slow and severity sometimes seems to level off and to progress no more — to ‘plateau’. Compared with other muscular dystrophies, FSH dystrophy is described as relatively benign and relatively slowly progressive.
Is FSH always inherited?
All muscular dystrophies are by definition inherited. An inherited disease is one which is due to a defect in the genetic material which is put together from the father's sperm and mother's ovum (egg) at conception. FSH is inherited as an autosomal dominant disease. The son or daughter of an affected person is at 50 per cent risk of inheriting the defective gene. If he or she does inherit the defective gene, there is no way of predicting whether the result will be FSH of average severity, severe FSH or early onset or FSH of a very mild degree of disability.
Last Reviewed: 13 June 2007