Becker, Limb-Girdle and FSHD Muscular Dystrophy Explained

Becker, limb-girdle and FSHD: the adult muscular dystrophies nobody writes about

Almost all public attention on muscular dystrophy goes to Duchenne, and almost all the people living with muscular dystrophy in Australia have something else.

These are the adult-onset types: Becker, the limb-girdle dystrophies, facioscapulohumeral dystrophy, Emery-Dreifuss, oculopharyngeal and the distal dystrophies. They share a profile that makes them systematically under-served. Onset in adolescence or adulthood, so there is no paediatric service holding the care together. Slow progression, so nothing is urgent until it is. A diagnostic odyssey measured in years. Rare subtypes that a general neurologist may have seen once. And — the dangerous part — cardiac and respiratory risk that varies enormously by subtype and that gets missed in the types where the limb weakness is mild.

That last point is the reason this guide exists. In several of these conditions, the thing that will shorten somebody’s life is not their difficulty climbing stairs. It is a conduction defect in their heart that nobody has looked for, in a person who is still walking.

Myotonic dystrophy, which is the most common adult form, has a guide of its own because it is a multisystem condition rather than a muscle one.

Becker muscular dystrophy

The genetics. The same gene as Duchenne — DMD on the X chromosome — but the variant allows some partially functional dystrophin to be produced rather than none. That single difference accounts for everything.

Who it affects. Males, X-linked recessive, with female carriers. Carrier women need cardiac surveillance of their own, covered in families, carriers and genetics.

The course. Enormously variable, and this is the defining feature. Onset ranges from childhood to middle age. Some men are diagnosed in their teens and use a wheelchair in their thirties; others are diagnosed at forty after an incidental finding and remain walking into their sixties. Progression is generally slow.

How it presents. Proximal weakness — hips and thighs first, then shoulders. Difficulty with stairs and rising from a chair. Calf hypertrophy, often prominent. Muscle cramps and exercise intolerance. Sometimes the first presentation is simply a raised creatine kinase found on a blood test done for something else, or raised liver enzymes that turn out to be muscle-derived.

And the cardiac issue, which is the critical point. Cardiac involvement in Becker does not track the severity of the limb weakness. A man with mild weakness who is still working and walking can have significant dilated cardiomyopathy. There are men whose first medical contact is a cardiology clinic, with heart failure, before any muscle condition has been identified. This disconnection is well recognised and it means cardiac surveillance in Becker is mandatory regardless of how well somebody is doing physically.

What surveillance should look like. Baseline cardiac assessment at diagnosis with ECG and imaging, then regular review — the interval set by your cardiologist, and at least annually once any abnormality appears. Cardiac MRI detects fibrosis before the ejection fraction drops. Medication started when indicated rather than once symptoms appear.

The practical instruction for anybody with Becker: if you have not had cardiac imaging in the last year, ask for it, whatever your mobility is like.

Limb-girdle muscular dystrophy (LGMD)

Not one condition. More than thirty genetically distinct subtypes, grouped together because they share a pattern: weakness beginning in the shoulder girdle and the hip girdle.

Inheritance. Both patterns occur. The dominant forms (now labelled LGMD D) are passed from one affected parent with a 50 per cent risk to each child. The recessive forms (LGMD R) require a faulty copy from each parent, which means parents are usually unaffected carriers, siblings have a 25 per cent risk, and there is frequently no family history at all. This is why LGMD is so often a surprise.

The proteins involved include calpain-3, dysferlin, the sarcoglycans, anoctamin-5, FKRP and many others. The subtype is identified by genetic testing, usually a neuromuscular gene panel.

Why the subtype matters more here than anywhere else. The subtypes differ in:

Age of onset, from early childhood to the fifties.

Rate of progression, from barely perceptible over decades to loss of walking within fifteen years.

Cardiac risk. Some LGMD subtypes carry substantial risk of cardiomyopathy or conduction disease; others carry essentially none. Which ones is subtype-specific knowledge.

Respiratory risk. Several subtypes involve diaphragm weakness, sometimes disproportionate to limb weakness — so somebody still walking can have significant nocturnal hypoventilation. Others do not.

Specific features. Some involve calf hypertrophy, some scapular winging, some early contractures, some prominent back pain, some a raised CK of many thousands in a nearly asymptomatic person.

So the single most useful thing somebody with LGMD can do is find out which subtype they have. “Limb-girdle muscular dystrophy” without a subtype does not tell a clinician what to monitor. If you were diagnosed before modern gene panels were available — which means before roughly the mid-2010s — it is worth asking whether re-testing would identify your subtype now. The yield from modern panels is considerably higher than from the targeted testing available a decade ago, and a subtype diagnosis changes the surveillance plan and may change treatment eligibility.

What to ask for: the specific gene and variant in writing; a cardiac and respiratory assessment appropriate to that subtype; and referral to a neuromuscular clinic rather than general neurology, because subtype-specific knowledge is where the value is.

Facioscapulohumeral muscular dystrophy (FSHD)

The name describes it: face, scapula, humerus. One of the more common muscular dystrophies in adults.

Inheritance. Autosomal dominant in the great majority, so each child of an affected person has a 50 per cent risk. The genetics is unusual — it involves a contraction of a repeat array on chromosome 4 that de-represses a gene called DUX4 — and a minority of cases arise from a different mechanism (FSHD type 2). New mutations occur.

Onset. Typically teens to twenties, though it ranges from infancy to late adulthood.

What it looks like, and the features that identify it:

Facial weakness, often first noticed as difficulty whistling, drinking through a straw, or an inability to close the eyes fully during sleep. A flat smile.

Scapular winging. The shoulder blades stand away from the chest wall, visibly, and the arms cannot be raised above the head because the scapula is not stabilised.

Striking asymmetry. This is characteristic and useful diagnostically — one shoulder, one arm, one leg substantially more affected than the other. Few other muscular dystrophies do this.

Foot drop, from anterior tibial weakness, often an early sign.

Abdominal weakness, which can cause a protruding abdomen and a positive Beevor’s sign.

Pain, which is commonly the most troublesome symptom and systematically under-treated. Shoulder and back pain from altered mechanics.

Hearing loss and retinal vascular changes in a minority, which is why hearing and eye assessments are recommended.

Prognosis. Usually slow progression with normal life expectancy. A substantial minority become significantly disabled and a smaller number use a wheelchair. Severity within a family varies widely, which makes counselling difficult and makes predictions unreliable.

Respiratory involvement is uncommon but occurs, particularly in those more severely affected, and respiratory function should be checked rather than assumed normal.

Cardiac involvement is generally not a major feature, which is a genuine difference from several other dystrophies — though it does not mean cardiac symptoms should be ignored.

What helps. Pain management, taken seriously. Physiotherapy. Ankle-foot orthoses for foot drop, which transform walking for many people. Scapular fixation surgery in selected cases, which can restore useful arm elevation and is worth asking about. Eye protection where the lids do not close fully at night. Hearing assessment.

Emery-Dreifuss muscular dystrophy

Worth its own section despite being rare, because it is the type where getting it wrong is most dangerous.

The triad: early contractures (elbows, Achilles tendons and the neck and spine, often before significant weakness), slowly progressive weakness in a humeroperoneal pattern, and cardiac conduction disease.

The cardiac part is the whole point. Conduction defects — atrial arrhythmias, heart block, sinus node disease — develop frequently and can cause sudden death. Many people need a pacemaker, and some need an implantable defibrillator. The cardiac disease can be the first and most serious manifestation, in somebody whose muscle weakness is mild.

Inheritance can be X-linked (emerin) or autosomal dominant (lamin A/C), and the lamin A/C forms in particular carry significant arrhythmia and cardiomyopathy risk.

The instruction is simple and it is urgent: anybody with Emery-Dreifuss muscular dystrophy, or with contractures and weakness of unexplained cause, needs cardiology involvement from diagnosis, with ECG, Holter monitoring and imaging, and ongoing surveillance. First-degree relatives should be assessed too, because an unaffected-looking relative carrying a lamin A/C variant can still be at arrhythmia risk.

Oculopharyngeal and distal dystrophies

Oculopharyngeal muscular dystrophy (OPMD). Late onset, typically after fifty. Autosomal dominant in most cases. It affects the eyelids — progressive ptosis, drooping lids that eventually obstruct vision — and the throat, causing dysphagia. The swallowing difficulty is the dangerous part: aspiration, weight loss and chest infections. Management includes eyelid surgery for the ptosis, speech pathology and dietetic input, and in some cases procedures to improve swallowing. Because onset is after fifty, many people with OPMD are outside the NDIS, which is a significant practical problem covered below.

Distal muscular dystrophies. A group affecting the hands, forearms, lower legs and feet first, rather than the girdles. Onset from the teens to late adulthood depending on subtype. Hand function and foot drop are the main issues, and the subtype again determines cardiac and respiratory risk.

The practical problems these types share

The diagnostic delay. Adults with slowly progressive weakness get told they are unfit, overweight, getting older, or anxious. Many are investigated for other things first. A raised creatine kinase is the thing that should prompt referral, and the single most useful request is: “can I have a CK test and, if it is raised, a referral to a neuromuscular clinic?”

Nobody holds the picture. No paediatric service ever held it, and adult care is fragmented by organ. A GP willing to coordinate is the most valuable relationship available.

Surveillance is not delivered unless requested. This is the recurring danger. The cardiac and respiratory assessments that these conditions require happen because somebody asks for them. Know your subtype’s protocol and track it yourself.

The NDIS age limit. Access depends on age at application, with a hard cut-off at 65 and no exception. For conditions with onset in the forties and fifties, this is usually fine. For oculopharyngeal muscular dystrophy, with onset typically after fifty, and for the later-onset limb-girdle subtypes, it is a real risk — a diagnostic delay of five years in somebody who became symptomatic at 58 can put them past the deadline. If you are over 60 with a progressive muscle condition and not an NDIS participant, apply now rather than waiting for the diagnosis to be finalised. See muscular dystrophy and the NDIS.

Work. Most people with these conditions are working age and want to keep working. Reasonable adjustments are an employer obligation under the Disability Discrimination Act, and JobAccess and the Employment Assistance Fund pay for workplace modifications and assistive technology. Do not resign before taking advice on income protection and total and permanent disablement cover, because many policies require a claim to arise while employed.

Pain and fatigue, which dominate daily life in several of these conditions and are the symptoms least likely to be addressed. Both are legitimate reasons to ask for specialist referral.

And the genetic conversation, which is different for every type. Dominant types carry a 50 per cent risk to each child; recessive types mean siblings are at 25 per cent and children usually unaffected; X-linked types affect sons through carrier daughters. Genetic counselling is free through state genetic services and is worth having whatever the type. See families, carriers and genetics.

Getting a diagnosis as an adult

The diagnostic journey in adult-onset muscular dystrophy is long, and knowing the shape of it helps you shorten it.

Why it takes years. Slowly progressive weakness in an adult produces no alarming moment. The commonest explanations offered are deconditioning, weight, age, anxiety and depression, and all of them are statistically more likely than a muscular dystrophy. People adapt — stop using stairs, avoid the gym, change how they get out of a chair — so by the time they present, they have normalised a substantial loss.

The test that redirects everything is a creatine kinase (CK) blood test. Cheap, available at any pathology lab, orderable by any GP. In most muscular dystrophies it is raised, sometimes to many thousands, and in some subtypes a markedly raised CK appears in a nearly asymptomatic person. A raised CK in an adult with weakness is a referral to a neuromuscular clinic, not a repeat test in six months.

What the pathway looks like after that. Neurological examination, which identifies the pattern — proximal versus distal, symmetrical versus asymmetrical, facial involvement, scapular winging, calf hypertrophy, contractures. Electromyography and nerve conduction studies, to distinguish muscle disease from nerve disease, which is the branch point that separates muscular dystrophy from motor neurone disease and the neuropathies. A neuromuscular gene panel, which has largely replaced muscle biopsy and which tests dozens or hundreds of genes at once. Muscle MRI in some centres, which shows the pattern of muscle involvement and can point towards particular subtypes. Muscle biopsy, now reserved for cases the genetics does not resolve or where an inflammatory myopathy is in question.

What gets excluded along the way, and some of it is treatable: inflammatory myopathies such as polymyositis and dermatomyositis, which respond to immunosuppression; myasthenia gravis; metabolic and mitochondrial myopathies; thyroid disease; severe vitamin D deficiency; and statin-related myopathy.

What to ask for, in these words. “Can I have a creatine kinase test?” Then, if it is raised: “Can I be referred to a neuromuscular clinic rather than general neurology, and can I have a neuromuscular gene panel?” Then: “Can I have the specific gene and variant in writing?” That last request is what makes the surveillance plan, the family counselling and any future treatment eligibility possible.