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Facioscapulohumeral Muscular Dystrophy

Facioscapulohumeral muscular dystrophy is a genetic disorder characterized by progressive weakness and atrophy of facial, shoulder and upper arm musculature.


Presentation

Symptom onset typically occurs during the second decade of life. Rare, severe cases may be associated with muscle dystrophy in childhood [7]; some patients may not present any symptoms until adulthood [8].

For unknown reasons, muscle weakness and atrophy is generally asymmetric.

Initially, muscle weakness affects facial muscles orbicularis oris, orbicularis oculi and zygomaticus. Consequently, movements requiring contraction of these muscles are restricted. The orbicularis oris muscle encircles the mouth and is needed to bring one's lips forward in order to whistle, drink from a straw, pronounce certain labial sounds or to adopt a mimic expression of surprise. Lid closure is mediated by the orbicularis oculi muscle. FSHD patients are frequently unable to completely close their eyelids, a condition that brings forward the additional issue of insufficient distribution of lacrimal fluid over the cornea. This may lead to dry eyes and ultimately to keratoconjunctivitis sicca. Finally, contraction of the zygomaticus muscle results in an upward movement of the mouth's angles while smiling. This expression may be lost in individuals suffering from FSHD.

Most patients develop shoulder weakness within a short period of time after symptom onset. The deltoid muscle is usually not affected. Scapula alata, i.e., wing-like protrusion of the patient's shoulder blades, is the most characteristic symptom of scapular involvement. The spine of the scapula is generally well visible. Shoulder weakness limits the patient's ability to lift any object above their head, even their own arms. External upper arm rotation and - with onset of humeral muscle dystrophy - additional arm movements are impaired.

Abdominal muscles, pelvic muscles and musculature of the lower leg may be affect during later stages of the disease. Because abdominal muscles play a major role in maintenance of a healthy posture, weakness of those muscles may lead to lordosis. Of note, lower abdominal muscles are generally more severely affected than upper abdominal muscles, which results in the Beevor sign. With regards to muscles of the pelvic region, adduction and abduction of the lower limbs may be restricted as well as extension of the hip joint. Loss of contractility of lower leg muscles may interfere with ankle flexion and cause foot drop, a condition associated with a characteristic alteration of gait and an increased risk of falls.

In rare cases, mild hearing loss and vascular retinopathy may be present [7]. Patients don't usually claim hearing or visual impairment to interfere with their everyday life. Severe cases of FSHD have also been related with epilepsy and mental retardation [9].

Leg Swelling
  • Leg swelling developed a few weeks prior to presentation. Intrauterine life and early childhood were uneventful while her family history was unremarkable.[ncbi.nlm.nih.gov]
Malocclusion
  • Patients may also exhibit dental malocclusions. This article presents the prosthodontic treatment for an 18-year old male with FSHD.[ncbi.nlm.nih.gov]
Muscle Weakness
  • This study will investigate the contribution of sarcomeric protein dysfunction to the pathogenesis of muscle weakness in FSHD.[ncbi.nlm.nih.gov]
  • Patients present with muscle weakness in these anatomic areas. The muscle weakness eventually spreads to other skeletal muscles as well. Landouzy Dejerine muscular dystrophy Landouzy-Dejerine muscular dystrophy Muscular dystrophy, Landouzy-Dejerine[wikidata.org]
  • Many genes may be incorrectly regulated in affected muscle tissue, but the mechanisms responsible for the progressive muscle weakness remain largely unknown.[ncbi.nlm.nih.gov]
  • Facioscapulohumeral muscular dystrophy is a muscle weakness and loss of muscle tissue that gets worse over time. Facioscapulohumeral muscular dystrophy affects the upper body.[nlm.nih.gov]
  • BACKGROUND: Although it is known that muscle weakness is a major cause of postural instability and leads to an increased incidence of falls in patients with neuromuscular disease, the relative contribution of lower extremity and trunk muscle weakness[ncbi.nlm.nih.gov]
Myopathy
  • OBJECTIVES: To report cases of chronic autoimmune necrotizing myopathy with anti-signal recognition particle antibodies (anti-SRP myopathy) initially misdiagnosed as muscular dystrophy, in particular, facioscapulohumeral muscular dystrophy (FSHD).[ncbi.nlm.nih.gov]
  • Rimmed vacuoles (RV) are a characteristic pathological feature in inclusion body myositis, but may also occur in other neuromuscular disorders, such as distal myopathies, oculopharyngeal myopathy, polymyositis, rigid spine syndrome, congenital myopathies[ncbi.nlm.nih.gov]
  • In conclusion, we suggest considering FSHD in the differential diagnosis of adult-onset distal myopathies with rimmed vacuoles.[ncbi.nlm.nih.gov]
  • The overall involvement appears to be disease-specific in FSHD as it significantly differed from that encountered in the other myopathies.[ncbi.nlm.nih.gov]
  • Taken together, the presenting features suggested both, a neuropathy and a myopathy.[ncbi.nlm.nih.gov]
Winged Scapula
  • RESULTS: All 6 patients were initially diagnosed with muscular dystrophy because of the long-term clinical course and lack of inflammation on biopsy; 5 were diagnosed with FSHD based on a winged scapula.[ncbi.nlm.nih.gov]
  • Surgery to fix a winged scapula. Walking aids and foot support devices if there is ankle weakness. BiPAP to help breathing. Oxygen alone should be avoided in patients with a high CO2 (hypercarbia).[nlm.nih.gov]
  • Most patients with shoulder weakness and winged scapulae preserve function of the deltoid muscle.[symptoma.com]
  • Other possible treatments include: Oral albuterol to increase muscle mass (but not strength) Speech therapy Surgery to fix a winged scapula Walking aids and foot support devices Outlook (Prognosis) Disability is often minor.[ufhealth.org]
Proximal Muscle Weakness
  • We report a 12-year-old patient with mental impairment and proximal muscle weakness who had marked involvement of the shoulder girdle and facial muscles. CK levels were above 7000 U/l, multiplex PCR dystrophin gene deletion screening was negative.[ncbi.nlm.nih.gov]
  • Individuals in the two unlinked families met the clinical criteria for the diagnosis of FSHD, including facial weakness, clavicular flattening, scapula winging, proximal muscle weakness, and myopathic changes on muscle biopsies without inflammatory or[ncbi.nlm.nih.gov]
  • Patients typically present with slowly progressive, symmetric, proximal muscle weakness with or without facial involvement and diminished or absent tendon reflexes. The pelvic or the shoulder girdle muscles can be affected first.[merckmanuals.com]
Myopathic Facies
  • Begins with weakness of the muscles of the face and shoulder girdle, causing inability to raise the arms above the head (in female, noticed while combing hair), myopathic facies, eyelids that remain partly open in sleep, and inability to whistle or to[whonamedit.com]
Limb Weakness
  • Unusual presentations included: foot drop in 16 (13%) and proximal lower limb weakness in eight patients (7%).[ncbi.nlm.nih.gov]
  • Most of the patients have FSHD type 1 (91.7 %), and weakness of the facial (59.2 %) was the most prevalent symptom at onset, followed by shoulder-girdle muscles (53.3 %) and distal (22.45 %) or proximal lower limb weakness (14.8 %). 85.57 % patients were[ncbi.nlm.nih.gov]
  • The symptoms of FSH dystrophy may appear during childhood with severe facial and limb weakness or develop slowly and gradually in adulthood with progressive difficulty closing the eyes, moving the face, lifting objects or walking.[kennedykrieger.org]
  • weakness until 60 years of age.[medlink.com]
  • The symptoms of FSH dystrophy may appear during childhood with severe facial and limb weakness or develop slowly and gradually in adulthood with difficulty such as eye closure, lifting or tripping.[hopkinsmedicine.org]
Facial Muscle Weakness
  • Typically the early symptoms include: Facial muscle weakness (Weakness of complete eye closure, difficulty smiling and whistling, problems pronouncing letters M, B and P) Shoulder blade muscle weakness (Difficulty lifting arms above head, prominent shoulder[facialpalsy.org.uk]
  • Typical Symptoms, seen in many but not all patients: Facial muscle weakness (eyelid drooping, inability to whistle, decreased facial expression, depressed or angry facial expression, difficulty pronouncing the letters M, B, and P) Shoulder girdle weakness[en.wikipedia.org]
  • The facial muscle weakness may be noticed as difficulty puckering the lips, smiling, sucking a straw, and closing the eyes while sleeping. Weakness may be asymmetrical, i.e. one shoulder may be weaker than the other shoulder.[encyclopedia.com]
  • Facial muscle weakness often makes it difficult to drink from a straw, whistle, or turn up the corners of the mouth when smiling.[ghr.nlm.nih.gov]
  • muscle weakness in all family members, as it could be shown in our F2 patients and in our patient with sporadic disease. 7 , 10 It is well known that in some families with typical FSHD, a proportion of clinically affected members may not have facial[jamanetwork.com]
Memory Impairment
  • OBJECTIVE: This study examines the prevalence of pain, fatigue, imbalance, memory impairment, and vision loss in persons with myotonic and facioscapulohumeral dystrophy and their association with functioning.[ncbi.nlm.nih.gov]
Profound Mental Retardation
  • In this patient, the involvement of facial muscle had been present since early childhood, but obscured due to the complication of profound mental retardation. Epilepsy emerged at eight years of age.[ncbi.nlm.nih.gov]
Neonatal Hypotonia
  • This 7-year-old girl had profound limitation of extraocular movements since birth, congenital facial diplegia, neonatal hypotonia, and progressive limb-girdle weakness.[ncbi.nlm.nih.gov]

Workup

The medical history of a patient's family generally implies FSHD upon detection of first symptoms. If a genetic screen has previously been conducted due to familial accumulation of the disease, the patient may even report genetic predisposition to muscle dystrophy. Tentative diagnosis of FSHD is confirmed by means of clinical examination.

Additional diagnostic measures may be indicated in case of doubt. The most reliable test is a genetic screen for FSDH1- or FSDH2-associated gene defects. Laboratory analyses of blood samples should reveal elevated levels of creatine kinase. Additionally carbonic anhydrase and troponin I have been proposed as biomarkers of FSHD [10]. Electromyography may be carried out and should prove reduced electrical activity of affected muscles. Muscle biopsies are not indicated unless the aforementioned tests provide results not consistent with FSHD.

Treatment

To date, there is no causative therapy for FSHD.

A variety of drugs has been tested for their efficacy in FSHD and recently, histone methylation has been proposed as a new target of therapy. Promising results have not yet been published. Although sympathomimetics may slightly increase lean body mass, muscle and grip strength, benefits don't outweigh possible side effects. Initially, similar effects have been reported for supplementation of creatine monohydrate, but results could not be confirmed in later studies.

Most patients with shoulder weakness and winged scapulae preserve function of the deltoid muscle. If that's the case, shoulder blades may be fixed against the thoracic wall by means of scapulothoracic arthrodesis in order to improve upper limb function [11].

Patients suffering from walking difficulties due to foot drop may benefit from an ankle-foot orthosis. It should be well adapted to the patient's anatomy. In severe cases, i.e., if control of knee movements is also reduced, orthoses should involve the knee joints.

Patients should be encouraged to realize low-intensity aerobic exercises [12].

Prognosis

Since the degree of repeat contraction on chromosome 4 has been related to the severity of FSDH1, genetic analysis may allow for an estimation of the outcome in a particular case of this type of muscle dystrophy. Shorter fragments and less repeats increase the likelihood of severe FSHD.

Muscle weakness and atrophy typically spreads from face to shoulders and upper arms. Little can be done to stop that progress. According to current knowledge, it is not possible to predict involvement of pelvic and lower leg musculature. Cardiac and respiratory muscle function are generally not compromised by FSHD. Thus, many patients may require a wheelchair at some point in their lives, but overall life expectancy is not reduced.

Etiology

FSHD is a genetic disorder inherited with an autosomal dominant trait. Penetrance is incomplete [2].

About 95% of all FSHD patients present a decreased number of certain sequence repeats on the long arm of chromosome 4 (position 4q35) [3], but a gene mutation causing that phenomenon has not yet been identified. Molecular biological analysis of DNA samples obtained from more than 150 FSHD patients revealed an inverse correlation between the number of macrosatellite D4Z4 repeats and the likelihood of severe FSHD [2]. While up to 100 D4Z4 repeats - each measuring about 3 kb in length - are considered physiological, FSHD patients present only 10 or even less. In detail, restriction digest yielded an Eco RI fragment larger than 30 kb in most healthy individuals, while more than 50% of test subjects with a fragment measuring less than 20 kb developed severe muscle dystrophy. Eco RI fragments shorter than 15 kb were associated with severe FSHD in all cases. Interestingly, complete absence of D4Z4 does not result in FSHD.

The majority of the remaining 5% of FSHD cases can be ascribed to mutations of gene SMCHD1 (structural maintenance of chromosomes flexible hinge domain containing 1), which is ubicated on the short arm of chromosome 18 (position 18p11).

Of note, few FSHD patients don't present either of the aforementioned genetic defects. To date, these cases are deemed sporadic. Possibly, they are related to as of yet undefined gene variants. Also, epigenetic mechanisms have repeatedly been proposed to contribute to severity of FSHD. Their precise pathogenetic role is still unclear and it is not known whether epigenetic modifications may cause a possible third type of the disease without an underlying sequence alteration being present.

Epidemiology

FSHD is the third most common heritable muscle dystrophy. Its prevalence has been estimated to be about 5 per 100,000 individuals, a rate only surpassed by myotonic muscular dystrophy and Duchenne muscular dystrophy [4].

No racial predilections have been described.

It has been reported that males are more frequently affected than females. Inheritance doesn't account for this observation, which consequently requires further verification, but may give important hints as to underlying pathogenetic mechanisms.

Most patients diagnosed with FSHD are adolescents.

Sex distribution
Age distribution

Pathophysiology

In FSHD1, reduced numbers of macrosatellite D4Z4 repeats in chromosome 4 cause hypomethylation and chromatin relaxation of that same chromosome. This is associated with loss of heterochromatic features, i.e., binding to histones and other proteins that render DNA rather inactive. Repeat contractions are therefore linked to increased expression of certain genes, namely of DUX4 (double homeobox 4). The DUX4 gene encodes for a sequence-specific transcription factor. DUX4 expression is generally considered "toxic" since it may interfere with myogenesis, trigger myocyte apoptosis and cause myositis [5]. Other genes whose expression may be elevated in FSHD1 patients are ANT1 (adenine nucleotide translocase type 1), FRG1 and FRG2 (FSHD region gene 1 and 2).

It has been proposed that diminished numbers of D4Z4 repeats in chromosome 4 are not sufficient to induce FSHD1. Instead, single-nucleotide polymorphisms in the chromosomal region distal to the last D4Z4 repeat seem to cause stabilization of DUX4 transcripts [6]. According to current knowledge, both repeat contractions and single-nucleotide polymorphisms are required for induction of muscle dystrophy.

Mutation of SMCHD1, located on chromosome 18 and responsible for FSHD2, also causes hypomethylation and chromatin relaxation of chromosome 4. Thus, it triggers the same pathogenetic mechanisms as described for D4Z4 repeat contraction. This explains why two genetic defects provoke identical symptoms of muscle dystrophy.

Prevention

No specific measures can be recommended to prevent FSHD.

Summary

Facioscapulohumeral muscular dystrophy (FSHD) is a rather common genetic disorder associated with metabolic and structural alterations of facial, shoulder and upper arm musculature that lead to progressive weakening and atrophy of the corresponding muscles [1].

Most cases can be ascribed to determined gene defects, while a minority of FSHD cases is deemed sporadic. Presumably, the latter also result from genetic disorders that have, however, not yet been characterized in detail. According to the gene variant causing FSHD in a determined patient, two types of the disease may be distinguished: FSHD1 is triggered by alterations on chromosome 4, FSHD2 results from gene variants located on chromosome 18. They don't differ in clinical presentation.

Symptom onset usually occurs during the second decade of life, but severe cases may already be diagnosed in childhood and sometimes, muscle weakness is not observed before adulthood. The disease typically spreads in an asymmetric manner, from facial muscles to shoulders and upper arms and within several years or decades. Affected individuals may initially report difficulties to perform tasks like whistling, drinking from a straw, smiling, grimacing or pronunciation of determined sounds. Eyelid movements may be affected and if lid closure is incomplete, patients may present with dry eyes or keratoconjunctivitis sicca. As soon as muscle dystrophy reaches the shoulder's musculature, arm power starts to diminish. It may become impossible for an FSHD patient to raise their arms or other weights above their head. External rotation of the upper arm is restricted. Over time, muscle atrophy may lead to winged scapulae and a pronounced scapular spine. Involvement of upper arm muscles further limits the patient's ability to perform day-to-day activities that depend on minimal arm power. In some cases, muscle dystrophy spreads even further and affects the pelvic region or lower legs, which causes difficulties while walking, running or climbing stairs. Some FSHD patients may need to use a wheelchair. To date, the reasons for FSHD-associated selective impairment of muscle function are not known.

Causative treatment for FSHD is not available. Supportive therapy mainly consists in orthopedic measures that compensate for the loss of muscle function.

Patient Information

Facioscapulohumeral muscular dystrophy (FSHD) is a rather common genetic disorder characterized by progressive weakening and wasting of facial, shoulder and upper arm muscles.

Causes

FSHD is a genetic disorder inherited with an autosomal dominant trait, i.e., if one parent inherits a mutated gene to their child, the presumably healthy gene inherited from the other parent is not able to compensate the defect. Men and women may both be affected by this disease.

Two genes have been identified as possible causes of FSHD. Both alter gene expression and muscle cell metabolism, which ultimately leads to muscle cell death, muscle weakness and atrophy.

Symptoms

Symptom onset usually occurs during the second decade of life, rarely in infancy or adulthood. Facial muscles are affect first. Subsequently, shoulder and upper arm muscles are compromised. In some patients, the disease may even lead to functional impairment of musculature of the pelvic region and lower legs.

The following symptoms may be observed:

  • Inability to whistle, drink from a straw, pronounce labial sounds.
  • Incomplete lid closure.
  • Missing upward movement of mouth angles while smiling.
  • Difficulties lifting any weight or even the own arms above the head.
  • Problems while walking or climbing stairs.
  • Inability to move the toes or to lift the tip of the foot.

Diagnosis

Genetic screens and identification of the underlying gene defect confirm FSHD diagnosis. However, a familial history of FSHD and observation of characteristic symptoms does already prompt a strong suspicion.

Treatment

There is no causative treatment for FSHD. While orthopedic measures may compensate for muscle weakness in certain regions of the body, i.e., the inability to lift the tip of the foot may be countervailed with an ankle-foot orthosis, about one out of four FSHD patients will require a wheelchair within less than a decade.

Life expectancy is unaltered.

References

Article

  1. Tawil R. Facioscapulohumeral muscular dystrophy. Neurotherapeutics. 2008; 5(4):601-606.
  2. Ricci E, Galluzzi G, Deidda G, et al. Progress in the molecular diagnosis of facioscapulohumeral muscular dystrophy and correlation between the number of KpnI repeats at the 4q35 locus and clinical phenotype. Ann Neurol. 1999; 45(6):751-757.
  3. Statland J, Tawil R. Facioscapulohumeral muscular dystrophy. Neurol Clin. 2014; 32(3):721-728, ix.
  4. Theadom A, Rodrigues M, Roxburgh R, et al. Prevalence of muscular dystrophies: a systematic literature review. Neuroepidemiology. 2014; 43(3-4):259-268.
  5. Statland JM, Tawil R. Facioscapulohumeral muscular dystrophy: molecular pathological advances and future directions. Curr Opin Neurol. 2011; 24(5):423-428.
  6. Lemmers RJ, van der Vliet PJ, Klooster R, et al. A unifying genetic model for facioscapulohumeral muscular dystrophy. Science. 2010; 329(5999):1650-1653.
  7. Lee GD, Chen VM, Barnes AC, Goldman DR, Duker JS. Retinal telangiectasis detected during a vision screening examination in a child with hearing loss led to the diagnosis of facioscapulohumeral muscular dystrophy. J Aapos. 2014; 18(3):303-305.
  8. Rogers MT, Zhao F, Harper PS, Stephens D. Absence of hearing impairment in adult onset facioscapulohumeral muscular dystrophy. Neuromuscul Disord. 2002; 12(4):358-365.
  9. Grosso S, Mostardini R, Di Bartolo RM, Balestri P, Verrotti A. Epilepsy, speech delay, and mental retardation in facioscapulohumeral muscular dystrophy. Eur J Paediatr Neurol. 2011; 15(5):456-460.
  10. Petek LM, Rickard AM, Budech C, et al. A cross sectional study of two independent cohorts identifies serum biomarkers for facioscapulohumeral muscular dystrophy (FSHD). Neuromuscul Disord. 2016.
  11. Giannini S, Faldini C, Pagkrati S, et al. Fixation of winged scapula in facioscapulohumeral muscular dystrophy. Clin Med Res. 2007; 5(3):155-162.
  12. Olsen DB, Orngreen MC, Vissing J. Aerobic training improves exercise performance in facioscapulohumeral muscular dystrophy. Neurology. 2005; 64(6):1064-1066.

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Last updated: 2019-07-11 19:58