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Facioscapulohumeral muscular dystrophy
This condition typically begins in adolescence or early adulthood, causing gradual muscle weakness that starts in the face and shoulders before potentially spreading to other muscle groups. The severity and rate of progression vary considerably between individuals, even within the same family.
Overview
Facioscapulohumeral muscular dystrophy, commonly abbreviated to FSHD, is an inherited muscular dystrophy affecting skeletal muscle function in the United Kingdom and worldwide. The condition derives its name from the muscle groups initially affected: facial muscles (facio-), muscles around the shoulder blades (scapulo-), and upper arm muscles (humeral). Evidence suggests the prevalence ranges from approximately 1 in 8,000 to 1 in 20,000 individuals.
Most people with FSHD first notice symptoms during their teenage years or twenties, though onset can occur anywhere from early childhood through to middle age. The condition progresses gradually over many years, and the pattern of muscle involvement follows a characteristic sequence. Weakness typically begins asymmetrically, meaning one side of the body may be more affected than the other. Many individuals maintain the ability to walk throughout their lives, though some eventually require mobility aids. Life expectancy is generally not reduced, though quality of life can be significantly affected by progressive muscle weakness.
Symptoms & clinical features
The earliest signs often involve difficulty with facial expressions - individuals may find it hard to smile, whistle, or close their eyes completely during sleep. Some people notice their face appears less expressive or that drinking through a straw becomes challenging. Weakness around the shoulder blades causes the scapulae to protrude outwards, sometimes described as 'winging', and makes it difficult to raise the arms above shoulder height. Tasks like lifting objects onto high shelves or styling hair can become increasingly problematic.
As the condition progresses, weakness may extend to muscles in the upper arms, lower legs, and abdominal wall. Some individuals develop foot drop, where weakness in ankle muscles causes the foot to drag when walking. Hip girdle weakness can emerge in later stages, potentially affecting walking ability. The progression rate varies considerably - some people experience minimal disability across their lifetime, whilst others develop more significant limitations. Muscle pain and fatigue are common complaints that can substantially impact daily functioning, even when measurable weakness remains relatively mild.
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Affected organs
FSHD primarily affects skeletal muscles, which are the voluntary muscles responsible for movement. The condition shows a distinctive pattern, characteristically involving facial muscles, shoulder stabilisers, and upper arm muscles first. Unlike some other muscular dystrophies, FSHD typically spares the heart and respiratory muscles in most individuals, though occasional exceptions occur. The diaphragm and breathing muscles are rarely affected, meaning most people do not develop significant respiratory complications.
Beyond muscle tissue, some individuals experience additional features including hearing loss (usually mild and affecting high frequencies), retinal vascular abnormalities that seldom cause vision problems, and occasional lower back pain related to altered posture from muscle weakness. These extra-muscular features occur in a minority of affected individuals and are generally less significant than the muscle weakness itself.
Risks & severity
The severity spectrum for FSHD is exceptionally broad. Some individuals remain so mildly affected that they never seek medical attention or receive a formal diagnosis. At the other end of the spectrum, others eventually require wheelchair assistance, typically after several decades of progressive weakness. The majority experience intermediate severity, maintaining independent mobility but with varying degrees of functional limitation.
Age of onset influences prognosis - earlier symptom onset, particularly before age 10, generally predicts more rapid progression and greater eventual disability. However, predicting an individual's trajectory remains challenging even when family history is known, as progression rates vary substantially between relatives carrying the same genetic change. Some people reach a plateau where weakness stabilises for extended periods, whilst others experience steady but slow progression throughout adulthood.
Genetic causes
FSHD arises through an unusual genetic mechanism involving a region on chromosome 4 called D4Z4. Normally, multiple copies of a repetitive DNA element at this location help silence a nearby gene called DUX4, preventing it from becoming active in skeletal muscle tissue. The most common form, FSHD type 1, occurs when the number of these repetitive segments contracts below a critical threshold. This contraction undermines the silencing apparatus, permitting DUX4 to be expressed in muscle cells where its protein product causes cellular damage.
A less common variant, FSHD type 2, involves mutations in genes that help maintain the repressive state of the D4Z4 region through chemical modifications to DNA packaging. Despite different underlying genetic mechanisms, both types result in inappropriate DUX4 expression in muscle tissue, explaining why they produce similar clinical features. Understanding this shared pathway has opened research avenues focused on suppressing DUX4 activity as a potential therapeutic strategy.
Inheritance pattern
FSHD follows an autosomal dominant inheritance pattern, meaning an affected individual has a 50% chance of passing the condition to each child, regardless of the child's sex. However, the condition displays variable expressivity - family members who inherit the same genetic change may experience markedly different severity and age of onset. Some individuals carry the genetic alteration but never develop noticeable symptoms, a phenomenon called reduced penetrance.
Some cases represent new genetic changes not inherited from either parent. In these situations, neither parent carries the alteration, and the recurrence risk for future siblings is low. When an individual with a new change has children, however, the 50% inheritance risk applies. Genetic counselling can help families understand their specific situation and reproductive options.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosis typically begins when a GP or neurologist recognises the characteristic pattern of muscle weakness. Blood tests may show elevated creatine kinase levels, an enzyme released from damaged muscle, though levels are often only mildly raised in FSHD. Electromyography can demonstrate features consistent with a myopathy, helping distinguish FSHD from neurological conditions affecting nerves rather than muscles.
Genetic testing provides definitive confirmation. Specialised laboratories analyse the D4Z4 repeat region on chromosome 4, measuring repeat length to identify the contraction characteristic of FSHD type 1. If this test returns normal results but clinical suspicion remains high, additional testing can identify FSHD type 2. Within the NHS, referral to clinical genetics services enables access to appropriate testing through the Genomic Medicine Service. The condition is included in NHS testing panels under relevant R-codes (the NHS coding system for rare disease testing) for neuromuscular disorders.
Management & lifestyle
No treatment currently exists to halt or reverse the underlying muscle degeneration in FSHD. Management focuses on maintaining function, managing symptoms, and preventing complications. Physiotherapy plays a central role, with tailored exercise programmes helping preserve strength and flexibility without overworking affected muscles. Occupational therapy assessment can identify adaptive equipment and home modifications to maintain independence.
Orthotics such as ankle-foot devices can help with foot drop, whilst scapular stabilisation bracing occasionally provides benefit for shoulder weakness. Pain management strategies may include standard analgesics, though some individuals require specialist pain clinic input. Regular monitoring through neuromuscular clinics allows early detection of complications. Genetic counselling should be offered to discuss inheritance risks and reproductive options. Clinical trials investigating DUX4-targeting therapies are ongoing, and affected individuals may wish to discuss trial participation with their specialists.
UK care pathway
Within the NHS, individuals with suspected FSHD typically access care through their GP, who may refer to neurology services. Following clinical assessment, referral to regional neuromuscular specialist centres provides access to multidisciplinary team expertise. Genetic testing is coordinated through the NHS Genomic Medicine Service, with clinical genetics teams providing genetic counselling alongside testing. Testing criteria and relevant R-codes for neuromuscular conditions guide appropriate test requisition.
Once diagnosed, ongoing care usually involves periodic review in specialist neuromuscular clinics, with frequency determined by disease activity and individual needs. Genetic counsellors remain available to address questions about inheritance, family testing, and reproductive choices. Patient organisations such as Muscular Dystrophy UK provide additional support, information resources, and connections to the FSHD patient community.
Frequently asked questions
Will I definitely pass FSHD to my children?
Each child has a 50% chance of inheriting the genetic change, but inheriting it does not guarantee symptoms will develop, and severity varies greatly even within families. Genetic counselling can explore options including predictive testing and reproductive choices.
Should I avoid exercise if I have FSHD?
Moderate exercise is generally beneficial and helps maintain function, but overexertion can potentially worsen muscle damage. A physiotherapist with neuromuscular expertise can design a safe, individualised exercise programme balancing activity with adequate rest.
Will FSHD affect my heart or breathing?
The heart and breathing muscles are rarely affected in FSHD, unlike some other muscular dystrophies. Most individuals do not develop cardiac or respiratory complications, though periodic monitoring may be recommended depending on individual circumstances.
Is there any treatment that can stop FSHD progression?
Currently no treatment can halt the underlying muscle damage, though research into therapies targeting DUX4 is advancing. Management focuses on physiotherapy, symptom control, and maintaining quality of life whilst research continues towards disease-modifying treatments.
How quickly will my symptoms progress?
Progression rates vary enormously between individuals - some people experience very slow changes over decades whilst others notice more rapid worsening. Earlier onset generally suggests faster progression, but predicting an individual's course remains difficult even with family history.
References
- Tihaya MS, Mul K, Balog J. Facioscapulohumeral muscular dystrophy: the road to targeted therapies. Nature reviews. Neurology. 2023. PMID: 36627512
- Tawil R. Facioscapulohumeral muscular dystrophy. Handbook of clinical neurology. 2018. PMID: 29478599
- Mul K. Facioscapulohumeral Muscular Dystrophy. Continuum (Minneapolis, Minn.). 2022. PMID: 36537978
- Sacconi S, Salviati L, Desnuelle C. Facioscapulohumeral muscular dystrophy. Biochimica et biophysica acta. 2015. PMID: 24882751
- Statland J, Tawil R. Facioscapulohumeral muscular dystrophy. Neurologic clinics. 2014. PMID: 25037087
- Tawil R. Facioscapulohumeral muscular dystrophy. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics. 2008. PMID: 19019312
- Fecek C, Emmady PD. Facioscapulohumeral Muscular Dystrophy. 2023. PMID: 32644454
- Tawil R. Facioscapulohumeral muscular dystrophy. Current neurology and neuroscience reports. 2004. PMID: 14683629