Facioscapulohumeral muscular dystrophy (FSHD)

Overview

Facioscapulohumeral muscular dystrophy (FSHD) causes progressive weakness that mainly affects the face, shoulders and upper arms, usually becoming noticeable in early adulthood, though later or milder onset happens too. There are two known genetic types: type 1 (around 95% of cases, linked to changes in the D4Z4 region on chromosome 4) and type 2 (rarer, linked to the SMCHD1 gene, which affects the same D4Z4 region indirectly). A rarer, more aggressive childhood-onset form exists too, starting before age 10 and generally progressing faster with additional health complications.

Symptoms

How FSHD presents varies enormously — even between members of the same family — from lifelong mild symptoms to significant disability. Weakness typically starts in the face, shoulders and upper arms and can be noticeably worse on one side than the other. Shoulder weakness makes lifting the arms above shoulder height difficult and often causes the shoulder blades to protrude ('winging'); facial weakness can make it hard to close the eyes fully or purse the lips, and in severe cases can affect speech and facial expression.

Later on, weakness can spread to the trunk, spine and legs, sometimes producing an exaggerated inward curve of the lower back; weakness in the lower legs causes foot drop, making stairs and uneven ground harder, and changes gait to a backward-leaning, high-stepping pattern with more frequent falls. Some people eventually need a wheelchair for longer distances. Chronic musculoskeletal pain — particularly in the neck, shoulders and lower back — is common. Breathing is usually well preserved (only around 1 in 100 people need overnight ventilator support), though roughly 1 in 10 have some chest-wall weakness affecting lung function, which can occasionally cause daytime sleepiness, morning headaches, poor appetite or weight loss if it disturbs overnight breathing.

The rarer early-onset form adds its own features: more pronounced facial, shoulder and limb weakness, common hearing loss that can worsen over time, possible vision problems, occasional breathing or heart involvement, scoliosis, and sometimes mild learning or behavioural differences alongside fatigue and pain.

Inheritance and cause

FSHD is usually autosomal dominant — a single changed copy from either parent is enough — though some cases arise fresh with no family history. In type 1, a shortened repeat sequence in the D4Z4 region weakens what normally keeps a gene called DUX4 switched off; once active, DUX4 produces a protein that damages muscle cells from the inside. Type 2 reaches the same end point via a different route — a change in the SMCHD1 gene that also ends up switching DUX4 on.

Getting a diagnosis

A GP can refer to a neurologist, who combines a physical exam, family history and genetic testing — most cases are confirmed with a blood test.

Management and outlook

Care works best through a multidisciplinary team, usually led by a neurologist, tailored to each person's specific pattern, age of onset and severity. A specialist physiotherapist can advise on safe activity, build an exercise plan, and help manage fatigue and posture — staying active helps preserve strength in unaffected muscles and supports independence, provided there's proper recovery time afterwards.

Orthotic devices help with specific problems — ankle-foot supports for foot drop, shoulder supports for winging — and eye lubricants protect against dryness or corneal damage where eyelid closure is incomplete. A speech and language therapist can help if facial weakness affects speech. Breathing is monitored with FVC testing and overnight sleep studies where relevant, with chest physiotherapy or cough support if needed.

The early-onset form benefits from a broader team — neurologists, physiotherapists, audiologists, ophthalmologists, orthopaedic surgeons and genetic counsellors — given how much faster it can progress, with support spanning assistive devices, pain and fatigue management, hearing and vision care, scoliosis treatment, nutrition, and emotional support alongside regular check-ups.