Abstract
Facioscapulohumeral dystrophy (FSHD) is the third most common inherited muscular dystrophy after Duchenne dystrophy and myotonic dystrophy. Over the last decade, major advances have occurred in the understanding of the genetics of this disorder. Despite these advances, the exact mechanisms that lead to atrophy and weakness secondary to the genetic defect are still not understood. The purposes of this article are to increase awareness of FSHD among clinicians; to provide an update regarding the genetics, clinical features, natural history, and current management of FSHD; and to discuss opportunities for research.
Facioscapulohumeral dystrophy (FSHD) is the third most common inherited muscular dystrophy after Duchenne dystrophy and myotonic dystrophy.1 Facioscapulohumeral dystrophy, as the name implies, is characterized initially by weakness and atrophy of the facial, scapular, and humeral muscles. It is inherited as an autosomal dominant trait. Over the last decade, major advances have occurred in the understanding of the genetics of this disorder.2–4 These advances have led to molecular diagnostic tests and improved genetic counseling and have allowed prenatal testing.5–10 Despite these advances, the exact mechanisms that lead to atrophy and weakness secondary to the genetic defect are still not understood. Currently, there is no genetic or pharmaceutical11 curative treatment for this condition. The mainstay of management is treatment of symptomatic impairments, prevention of secondary problems, and improvement of functional abilities and quality of life within the constraints imposed by this progressive condition.12–14
Physical therapists are appropriately trained to play a major role in the management of FSHD. The purposes of this article are: (1) to increase awareness of FSHD among clinicians, (2) to provide an update regarding the genetics, clinical features, natural history, and current management of FSHD, and (3) to discuss opportunities for research.
Historical Developments
Facioscapulohumeral dystrophy was first described by 2 French physicians, Louis Landouzy and Joseph Dejerine, in the late 1800s; their description was based on a family that they had monitored for 11 years.15 Their publications described all the main elements of FSHD, including early involvement of the face, progressive weakness and atrophy of the scapular and humeral muscles, the hereditary nature of the disorder, and clinical variability among affected members of the same family. In 1950, Tyler and Stephens16 described a kindred from Utah that included 1,249 people spanning 6 generations. All were descendants of an affected individual who had migrated to Utah in 1840. The authors were able to examine 240 members of this family, 58 of whom were affected. Their report provided detailed inheritance and clinical information. Their findings confirmed the autosomal dominant inheritance pattern and the clinical heterogeneity of the disorder, as described by Landouzy and Dejerine. In 1982, on the basis of a retrospective review of 107 patients, Padberg17 provided detailed information regarding the presenting complaints, clinical progression, and laboratory findings in patients with FSHD.
Clinical criteria for the diagnosis of FSHD were established by an international consortium in 199118 and are as follows:
onset of the disease in the facial or shoulder girdle muscles and sparing of the extraocular, pharyngeal, and lingual muscles and the myocardium
facial muscle weakness in more than 50% of affected family members
autosomal dominant inheritance in familial cases
evidence of myopathic disease from electromyography and muscle biopsy in at least one affected member, without biopsy features specific for alternative diagnoses
Since the publication of these criteria, myocardial involvement has been documented.19,20
Since the establishment of these clinical diagnostic criteria, major advances have occurred in the area of genetics related to FSHD. These advances have provided molecular tests for the diagnosis of FSHD and improved genetic counseling for family members. The availability of molecular tests has also expanded the spectrum of presenting complaints and clinical phenotypes.
Genetic Developments
A glossary of genetic terms is provided in the Appendix.21 The FSHD locus was mapped to the subtelomeric portion of chromosome 4 (4q35) in 1990.2 This subtelomeric region is composed mainly of a polymorphic repeat structure consisting of 3.3-kilobase repeat elements designated D4Z4. The number of repeat units varies from 11 to more than 100 in the general population. In patients with FSHD, there is a deletion of an integral number of these units, and they exhibit an allele of 1 to 10 residual units.3 With the mapping of the FSHD locus, molecular diagnostic tests with a specificity and a sensitivity of 95% have become available.6,7,9,22 The tests are performed on DNA isolated from peripheral blood leukocytes and are available commercially. Facioscapulohumeral dystrophy has a high rate (10%–30%) of sporadic cases23; therefore, there may not be a family history of people who were affected. Ten percent of these sporadic cases are attributed to new mutations, and 20% are attributed to mosaicism.24
The genetic diagnostic tests do not allow precise prediction of the course of the disease in an individual, but an approximate and inverse relationship among the residual repeat size, the age at onset, and the severity of the disease has been described. Patients carrying 1 to 3 units are usually severely affected and often represent new mutations, whereas patients carrying 4 to 10 units are typically familial cases.25 However, because of the high degree of interfamilial and intrafamilial variability of disease expression in family members even with fragments of the same size, it is impossible to predict the disease severity and progression in a given individual. Despite all of the advances in the understanding of the genetics of the disease, the exact mechanisms responsible for the clinical features are still not known.26
Prevalence
On the basis of the studies of Padberg and colleagues,17,27 the prevalence of FSHD in the Dutch population in the Netherlands is estimated to be 1 in 21,000. For the United States, Flanigan et al28 reported a prevalence of 1 in 15,000 in the Utah-southern Idaho region, on the basis of their follow-up of and findings for 971 additional members of the family first described by Tyler and Stephens.16
Clinical Features
The clinical presentation of FSHD is usually quite characteristic, with a majority of patients in the second or third decade having complaints related to difficulty with overhead activities. On the basis of a retrospective review of 107 patients, Padberg17 reported that 82% of patients noticed shoulder girdle weakness as the first symptom, 10% reported facial muscle weakness, and 8% reported ankle dorsiflexor muscle weakness. On examination, however, he found that 94% had facial muscle weakness, 93% had shoulder girdle weakness, 67% had ankle dorsiflexor muscle weakness, and 50% had pelvic girdle weakness. Recently, Padberg29 reported that 5% of patients report symptoms related to pelvic girdle weakness as their initial symptoms. This information is important because symptoms or signs of pelvic girdle weakness may confuse the clinical diagnosis of FSHD with limb girdle dystrophies, especially in the absence of facial muscle weakness.
With the availability of molecular diagnostic tests, a broader spectrum of clinical presentations is being reported. Bushby et al30 described 4 patients in whom muscle pain was a prominent complaint. Van der Kooi et al31 described 6 cases in which 3 patients had foot drop, 2 had walking difficulty, and 1 had shoulder pain. On examination, 1 of the 2 patients with walking difficulty had calf muscle weakness, and the other patient had quadriceps femoris and hamstring muscle weakness. Felice and Moore32 described 4 patients with atypical presentations: 1 with facial muscle sparing and scapular myopathy, 1 with limb girdle involvement, 1 with distal myopathy, and 1 with asymmetric brachial weakness. Even though the most common presenting complaints of FSHD are related to scapular muscle and shoulder girdle involvement, symptoms or signs of weakness of facial muscles, the pelvic girdle, or lower-extremity muscles or all of these in a patient in the presence or absence of a family history of similar problems require a thorough examination and, if necessary, a medical referral to rule out FSHD.
Facial Muscle Weakness
The most commonly affected facial muscles are the orbicularis oculi and the orbicularis oris. Often the involvement around the lips is asymmetric. Recently, Wohlgemuth et al33 documented swallowing difficulties in 10 of 87 adult patients. Videofluoroscopic and magnetic resonance imaging examinations revealed atrophy or weakness or both of the tongue in 6 of these patients. The authors did not find any evidence of atrophy or deterioration of the pharyngeal or laryngeal muscles and concluded that the swallowing problems were secondary to the weakness of the orofacial muscles only.
Shoulder Girdle Weakness
On examination of the shoulder girdle, a striking feature is the elevated position of the scapulae because of weakness of the middle and lower trapezius muscles16 and internal rotation of the arms (Fig. 1). There is a flattening of the anterior chest wall, and 5% of patients have pectus excavatum.17 Atrophy of the pectoralis major muscle, especially the sternal head, and involvement of the clavicular portion of the sternocleidomastoid muscle also are early features of the disease16 (Fig. 2). On active shoulder flexion or abduction, there is marked winging of the scapula (Fig. 3). The weakness often is asymmetric, and this feature distinguishes FSHD from limb girdle dystrophies.
Elevated position of the scapulae and internal rotation of the arms are characteristic of facioscapulohumeral dystrophy.
Atrophy of the pectoralis major muscle, especially the sternal head, and involvement of the clavicular portion of the sternocleidomastoid muscle—early features of the disease.
Marked winging of the scapula on active shoulder flexion or abduction.
Abdominal Muscle Weakness
Abdominal muscle weakness is another early feature of the disease. The weakness results in a lordotic posture with a protuberant abdomen. The weakness is prominent in the lower abdominal muscles, and a positive Beevor sign (upward movement of the umbilicus on an attempt to sit up) has been reported in a majority of patients with FSHD.34,35 On the basis of their findings, the authors of those studies recommended considering a positive Beevor sign as an additional clinical criterion in confirming the diagnosis of FSHD.
Lower-Extremity Muscle Weakness
For the lower extremities, weakness has been reported in the ankle dorsiflexor muscles as well as the pelvic girdle.17,29 In a prospective natural history study in which 81 patients were monitored for 3 years, the investigators36 documented weakness in muscles usually considered to be spared in FSHD, such as the hamstring and quadriceps femoris muscles, in addition to marked weakness in the ankle dorsiflexor muscles. Olsen et al37 described findings from magnetic resonance imaging of lower-extremity muscles in 18 patients with FSHD. The most marked involvement was seen in the hamstring muscles, followed by the tibialis anterior and medial gastrocnemius muscles.
Progression of Weakness
According to Padberg,17 30% of all familial cases never progress beyond shoulder weakness. In the remaining cases, the next stage involves foot dorsiflexor muscle weakness in 80% or pelvic girdle weakness in 20%. These patterns are not restricted to certain families, and both patterns have been observed within the same family. At the same time, in the upper extremities, there is progression to the “humeral component”; the biceps and triceps muscles become weak and wasted. Eventually, the wrist extensor muscles are involved, resulting in a weak grip and functional limitations in activities of the hand. Approximately 10% of all patients and 20% of those more than 50 years of age will eventually become wheelchair dependent in outdoor activities. Patients usually live a normal life span, although about 20% are severely disabled because of weakness. The progression of weakness is very slow and occurs over decades, thus allowing patients to adapt and compensate for their weakness and continue to function.
Asymmetry of Weakness
Asymmetric weakness is characteristic of FSHD, but the reason underlying the sometimes extraordinary asymmetry is unknown. Various hypotheses have been proposed for the observation, including overwork weakness38 and handedness,39 whereas other authors have ascribed the asymmetry to an intrinsic disease process40 or to an intrinsic genetic mechanism.29 Despite the asymmetric weakness, the incidence of contractures or scoliosis is low. About 10% of patients with FSHD have ankle contractures, and 30% develop scoliosis.29
Cardiac and Pulmonary Features
In addition to the facial, abdominal, and extremity muscle weakness, pulmonary and cardiac involvement also has been documented. Wohlgemuth et al41 conducted a nationwide study in the Netherlands to investigate the prevalence of respiratory insufficiency in FSHD. They identified 10 patients who had FSHD and who were on nocturnal ventilatory support at home, representing approximately 1% of the Dutch population with FSHD. The risk factors that they identified included severe involvement with wheelchair confinement, moderate to severe kyphoscoliosis, and the presence of pectus excavatum. Galetta et al20 compared 24 patients with FSHD with 24 age-matched controls who were healthy and reported subclinical cardiac involvement in the patients with FSHD. Their findings suggested a preclinical reduction of left ventricular function and abnormal myocardial activity. Trevisan et al19 described findings from a multicenter study aimed at investigating cardiac involvement in patients with FSHD. Ten of the 83 patients (12%) demonstrated symptoms or signs of heart involvement, mainly arrhythmic in origin, in the absence of cardiovascular risk factors.
Extramuscular Features
In addition to the muscular involvement, retinal abnormalities42,43 and hearing loss also are associated with FSHD. Visual loss occurs in only a small minority of patients, but high-tone hearing loss29,43 has been described in 25% to 65% of patients.
Pain
Even though pain is not a symptom commonly mentioned in textbooks, pain is a symptom often reported by patients and described in recent case reports. A survey conducted in France44 showed that, out of 270 patients who responded (approximately 10% of the patients with FSHD in France), only 5% did not complain of pain and 32% reported pain as a daily problem. The exact nature and cause of the pain were not specified. A similar survey conducted in the Netherlands45 revealed that, out of 109 people who responded (approximately 18% of the patients with FSHD in the country), 74% experienced pain for more than 4 days per month and 58% did so for 4 or more days per week. The percentage of people who experienced daily pain was similar to that reported in the French survey, namely, 32%. The majority of the respondents attributed the pain to exertion (91%) or faulty posture (74%) because of weakness. Environmental temperature (48%) and humidity (27%) also had significant influences on the complaints related to pain. The various pain management techniques used by the respondents, including analgesics, hot baths or showers, and massage, provided only temporary relief. The respondents also reported that pain had a substantial effect on their well-being and functioning.
Fatigue
Kalkman et al46 surveyed the prevalence of severe fatigue and its relationship to functional impairments in daily life in 598 patients with a neuromuscular disease (139 with FSHD). Sixty-one percent of the patients with FSHD reported severe fatigue. These patients also reported reduced levels of physical activity and reduced motivation. The causes and mechanisms underlying the complaint of fatigue in FSHD are not well understood.
Infantile and Early-Onset Presentation
Although most patients with FSHD report having signs or symptoms in the second or third decade, infantile and early-onset presentations had been described since the late 1970s.47,48 Most early-onset cases are sporadic, with large deletions resulting in fragments with only 1 to 3 D4Z4 repeats. Some cases are occasionally diagnosed as Möbius syndrome. These patients often have normal motor milestones and develop signs of muscle weakness several years later.49,50 A report from Japan has indicated an association with mental retardation and epilepsy in people with an early onset who are severely affected.51
Management
Currently, there are no curative genetic or pharmaceutical treatments11 for this disease. The mainstay of management is care directed at the symptomatic impairments in order to maximize functional abilities and improve the quality of life of patients. Recommendations are usually based on expert opinion because there are very few studies, except in the areas of exercise and scapular surgery; even in those 2 areas, the majority of the studies are cohort studies or pilot open trials with inadequate numbers.
Facial Muscle Weakness
An inability to smile because of facial muscle weakness remains a major social disability in FSHD. Weakness of the labial muscles can lead to articulation difficulties in the later stages but does not progress to the point at which alternative means of communication become necessary. On the basis of their finding of swallowing difficulties, Wohlgemuth et al33 recommended that patients be referred to speech therapists for further evaluation of and teaching related to compensatory strategies for swallowing. Weakness of the orbicularis oculi can cause incomplete lid closure (lagophthalmos), which can lead to serious exposure keratitis and corneal scarring, major safety concerns. Eye drops, ointments, taping, or patches have not always been successful in managing these problems.42
Scapular Muscle Weakness
Scapular muscle weakness and the resulting difficulties with overhead activities are a major problem for patients. In addition to loss of function, marked winging of the scapula can lead to pain and cosmetic deformity. The force necessary to keep the scapula stabilized while still allowing appropriate mobility have made the use of taping, slings, and spinal orthoses difficult, except in a few cases. There is only one report in the literature describing the benefits of a spinal orthosis.52
A Cochrane review53 on the topic of scapular fixation in muscular dystrophy did not find any randomized or quasi-randomized trials of scapular fixation. Thus, the authors reviewed the case series and case reports related to scapular stabilization surgery in patients with FSHD. The 2 most commonly used procedures were scapulopexy (fascial or synthetic slings were used to improve scapular fixation to the thorax) and scapulodesis (the scapula was fixed to the thoracic wall with screws, wires, or plates, with or without a bone graft to produce a solid fusion). Both procedures resulted in significant improvements, as measured by improvement in shoulder abduction at 1 year and by patient-perceived improvement in the performance of activities of daily living. Some of the complications reported included stretching of the slings, loosening of the screws and wires, and—in some cases—nerve damage. The report recommended that each patient be evaluated thoroughly and that the benefits and complications be weighed carefully prior to making a decision regarding surgical treatment.
Abdominal Muscle Weakness and Lordosis
There are no reports in the literature of specific management techniques shown to be useful for improving posture or decreasing the discomfort secondary to the postural abnormality in patients with FSHD. Clinicians tend to recommend abdominal supports and binders54 for patients with marked weakness and appropriate postural supports and environmental adaptations when patients are seated.
Ankle Muscle Weakness
Foot drop attributable to ankle dorsiflexor muscle weakness is a common problem in patients with FSHD. There are no reports in the literature of the specific kinetic or kinematic patterns of gait seen in patients with FSHD to guide management. There also are no reports regarding algorithms for the timing or choice of specific types of ankle-foot orthoses and no reports regarding the benefits of these orthoses in patients with FSHD with regard to gait or functional abilities. Decisions regarding the timing and type of orthoses are based on empirical data and vary from clinician to clinician.12–14 The braces most commonly recommended include fixed or hinged ankle-foot orthoses or floor reaction orthoses.
Role of Exercise
The role of exercise in maintaining or improving strength (force-generating capacity) and function or both in patients with FSHD remains controversial because of concerns about overuse precipitating weakness and the limited number of clinical trials. The paucity of well-designed and appropriately powered studies of exercise in FSHD was highlighted in a recent Cochrane review55 of strength training and aerobic exercise training for muscle disease. The review identified 36 reports published between 1966 to 2004. Nineteen of these studies examined the effects of strength training, 9 studies examined the effects of aerobic training, and 8 studies examined the effects of a combination of strength training and aerobic training. Unfortunately, most of these studies had small numbers of patients, had a mixture of diagnostic categories, were of short duration, and were nonrandomized (32 of the 36). On the basis of the evidence from the 2 randomized controlled trials that met their criteria for inclusion, the authors concluded that moderate-intensity strength training does not produce any benefit or harm in patients with myotonic dystrophy56 or FSHD.57 Since the publication of the Cochrane review,55 Olsen et al58 reported the effects of a 12-week home program of aerobic training in 8 patients with FSHD and 7 age- and sex-matched volunteers who were healthy. On the basis of their findings, the authors concluded that low-intensity aerobic exercise improved fitness safely in patients with FSHD. The 12 weeks of training had positive effects in general on the self-reported measures of strength, endurance, and activity level.
Because of the limited literature on the effects of exercise training in patients with FSHD, clinicians have had to depend on consensus or empirical advice for their recommendations regarding exercise and activities for patients with muscle diseases. The current recommendations59–61 are as follows:
pursuit of an active lifestyle for its physical and psychological benefits
flexibility training including stretching and range-of-motion exercises, which may be helpful in decreasing the discomfort attributable to the limited mobility of the joints secondary to muscle weakness
moderate-intensity resistive strengthening exercise, which may be beneficial in reversing disuse weakness and improving strength during the early stages of the disorder in muscles that have antigravity or greater strength
moderate-intensity aerobic training programs, which may be beneficial in maintaining or improving aerobic capacity
The authors of these recommendations did not provide an operational definition of “moderate intensity” for either the strengthening or the aerobic fitness training programs. The reports on which they based their recommendations, most of which were cited in the Cochrane review,55 used a variety of training regimens in their strengthening and fitness programs. The strengthening programs used weights ranging from 20% to 70% of 1 resistance maximum, repetitions ranging from 5 to 12 per set, number of sets ranging from 1 to 4, and frequency ranging from 3 to 7 days per week. A similar diversity of regimens were used in the aerobic fitness training programs. The lack of standardization of the training regimens and the limited number of appropriately designed and powered studies provide immense opportunities for therapists to contribute to this area of care. The most urgent needs include the development of a consensus regarding testing, specifically, submaximal exercise testing,62 which may be more appropriate in patients with FSHD, and the development of training regimens that incorporate recommendations from the American College of Sports Medicine position stands.63–65
Therapists also can contribute to the literature by providing case reports and cohort studies documenting the role of physical therapy and physical therapists in the evaluation and management of FSHD. Specifically, they can report on the role of physical therapy interventions in treatment and management of pain; the role of orthotics in decreasing problems secondary to shoulder girdle, abdominal muscle, and ankle dorsiflexor muscle weakness; and the benefits of exercise in improving strength, aerobic fitness, functional abilities, mood, and quality of life.
Conclusion
Over the last decade, major advances have occurred in the understanding of the genetics and clinical features of FSHD. The exact molecular mechanisms underlying the disease remain elusive, and currently there is no cure for this disorder. Physical therapists can play a major role in the multidisciplinary management of FSHD by providing symptomatic and preventive care to minimize secondary complications and help patients function at their highest level within the constraints imposed by this progressive disorder. Therapists also can help build the evidence to support the efficacies of their interventions through case reports, retrospective and prospective cohort studies, and randomized controlled trials.
Footnotes
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Ms Pandya and Ms King provided concept/idea/project design. Ms Pandya provided writing. Dr Tawil provided consultation (including review of manuscript before submission).
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This work was partially supported by funding from the Paul D Wellstone Muscular Dystrophy Cooperative Research Center at the University of Rochester to Ms Pandya and Dr Tawil and a Delta Railroad Construction grant from the FSH Society to Ms Pandya and Ms King.
- Received April 4, 2007.
- Accepted August 20, 2007.
- Physical Therapy
References
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