Facioscapulohumeral Muscular Dystrophy

History

Facioscapulohumeral muscular dystrophy (FSH) was first described by Landouzy and Dejerine in 1885, and was therefore named after them. Duchenne had published a photograph of a typical FSH patient in 1862, 23 years earlier, but still the disease became known as Landouzy-Dejerine disease. From the beginning, FSH was recognized as an autosomal dominant disorder. This was confirmed, however, in 1950 by Tyler and Stephens, who conducted a large study based upon records from the Mormon church in Salt Lake City, Utah.

The exact nature of the disease, however, was a topic of heated debate for many years. The controversy centered around whether the muscle weakness and wasting was primarily from a neuropathic or myopathic cause. The debate was eventually settled in favor of a myopathic etiology, and in 1954, Walston and Nattrass included FSH as one of the three categories of muscular dystrophy, along with Duchenne MD and Limb-Girdle MD. FSH has survived as a distinct clinical entity, which was confirmed by the discovery that it is a distinct genetic disorder as well.

Clinical Presentation

FSH is a distinct type of muscular dystrophy, both clinically and genetically. When fully developed it presents with a characteristic pattern of muscle weakness, including, as the name implies, weakness of the facial muscles, the scapula, and the upper arms. The onset of noticeable symptoms usually occurs in childhood or young adulthood, but may rarely occur in middle life. An infantile onset form of FSH has also been described.

In most cases facial weakness is the first sign of the disease. The weakness results in an expressionless appearance. Patients soon develop an inability to smile, whistle, or fully close the eyes. The lips appear full and are often everted. The eyes may seem prominent and patients may also appear to sleep with their eyes partially open.

Weakness of the shoulder girdle - those muscles which stabilize the scapula to the torso (the trapezius, rhomboid, and the serratus anterior), result in an inability to elevate the arms. Attempts at moving the arms outward or forward results in winging of the scapulae. Patients will tend to adopt a characteristic posture with the shoulders thrust forward and the chest wall appearing flattened, due to pectoralis muscle atrophy. Arm weakness may be asymmetrical.

Biceps and triceps weakness in the arms completes the characteristic pattern. The deltoids are usually not weak, but may appear so when tested because of the unstable scapula. Wrist extension more so than wrist flexion weakness is also common. When the lower extremity muscles are affected, in contrast to the upper extremities, the weakness tends to be more distal than proximal, often resulting in foot drop. There may also be abdominal muscle weakness. Finally, in about 20% of patients, the weakness may spread to the pelvic girdle and rarely may involve the respiratory muscles. The combination of pelvic and abdominal muscle weakness often results in hyperlordosis - increased lumbar curvature of the spine - and protuberance of the abdomen.

In more that half of patients with FSH, weakness remains confined to the face and upper extremities and life expectancy is normal. In these cases, patients are often able to compensate quite well for their weakness. Those with pelvic girdle involvement may eventually become confined to a wheelchair, and the rare cases with respiratory involvement may have a diminished life expectancy.

Unlike many of the other muscular dystrophies, FSH is not associated with disease of other organ systems. Specifically, the heart is not involved and there is no association with mental retardation. There is an association with labile hypertension, although the reason for this is not understood. There is also in increased incidence of sensorineural hearing loss and Coats' disease, a disorder which includes detachment of the retina and telangiectasias.

Diagnosis

FSH is primarily diagnosed based on the clinical evaluation, including the presence of muscle weakness in the pattern described above with an appropriate age of onset and a family history indicating an autosomal dominant inheritance. Ocular and oropharyngeal weakness should be absent. The presence of contractures is also not consistent with the diagnosis. In addition, the following laboratory findings are supportive of the diagnosis:

  • Serum CPK - normal to mildly elevated (no more than 10 times normal)
  • Electromyography (EMG) - myopathic pattern with short muscle unit action potential duration and an increased recruitment pattern.
  • Electrocardiogram (ECG) - normal, unless there is coexistent cardiac disease
  • Muscle Biopsy - reveals isolated angular fibers, some necrotic fibers, and moderate endomysial connective tissue proliferation. These findings are multifocal, with some areas of the muscle appearing normal and others appearing severely affected. There may also be inflammatory cells seen.
  • Genetic Testing - DNA analysis for the chromosome 4q35 deletion, however this is positive in only 77% of FSH patients and is also positive in 21% of normal controls.

In order to confirm the diagnosis of FSH it is also necessary to exclude those disorders which may look like FSH. These include nemaline myopathy, mitochondrial myopathy, polymyositis, and inclusion body myositis. This distinction if often best made by muscle biopsy. Patients without facial weakness may also have either spinal muscular atrophy, Davidenkow's syndrome of scapuloperoneal neuropathy, or another form of muscular dystrophy. The diagnosis of FSH is excluded in those patients without facial weakness, unless there are affected family members who do have facial weakness.

Genetics

FSH is an autosomal dominant disorder with a prevalence of 1 in 20,000. Sporadic cases without a family history usually represent new mutations. FSH is due to a deletion which has been localized to the distal portion of the long arm of chromasome 4 (4q35). Expression of the FSH gene is variable. Although penetrance is 95% by age 20, there is a wide range of severity, even within families. A recent study by R Tawil et al (Annals of Neurology 1996 Vol.39 No 6 pg.744-48) indicates that the size of the 4q35 deletion corresponds to the severity of the disease and that such severity shows anticipation, meaning that it tends to increase in subsequent generations.

Treatment

There is currently no cure for FSH or treatment which alters the course of the disease. There are, however, treatments which are effective in improving the quality of life of FSH patients. Physical therapy is useful in maintaining the highest degree of function possible. For those with foot drop, an ankle-foot orthosis is often helpful. A surgical procedure to fix the scapula to the thorax (scapulothoracic arthrodesis) may result in improved deltoid strength and therefore upper arm function. This procedure, however, is usually restricted to those with mild disease. For those who are wheelchair bound, with weakness of abdominal muscles resulting in a protuberant abdomen, a corset or brace will often provide improved comfort. Having the proper equipment, such as a motorized chair with adjustable height, is also essential for maximizing comfort and independence.

Genetic counseling should also be considered for patients and families with FSH. Pre-natal testing is available, but because of the variable expression of FSH, it is not as useful or desirable as with other genetic disorders.

Support Groups

Muscular Dystrophy Association (MDA)
National Headquarters
3300 East Sunrise Drive
Tucson, Arizona 85718
Phone: 1-800-572-1717

The MDA supports research and patient care for over 40 diseases, including FSH. They can put patients and families in touch with local chapters and support groups.

Facioscapulohumeral Society, Inc. (FSH Society)
Contact: Carol A. Perez, Executive Director
3 Westwood Road
Lexington, MA 021713
Phone: 617-860-0501
Fax: 617-860-0599

The FSH Society was founded in 1989 and currently operates three chapters. They provide information for patients, families, the public and media, and for professionals. They also provide referrals to local chapters or groups for peer support.

Internet Links to other FSH sites

Disclaimer

This page is intended for educational purposes only, to provide an overview of FSH for patients, their families, and health care providers. It is not intended to recommend any specific treatment, nor should it be used as a guide for self-treatment. Patients with FSH should consult their physician before making any changes to their treatment regimen.