Facioscapulohumeral Muscular Dystrophy
Also known as: FSH MD; FSH Muscular Dystrophy
Facioscapulohumeral muscular dystrophy (FSHD) is a genetic muscle wasting condition. Weakness usually starts in muscles of the face (facio-), shoulder blade (scapulo-), and upper arm (humeral). However, other muscles, including of the spine, hips and legs, often also become weakened.
Last updated March 2015 by Dr P Lunt, Honorary Research Fellow, University of Bristol, Bristol, UK.
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Symptoms are often first recognised in late teenage years in shoulder muscles, but may start in earlier childhood or later adulthood. Facial weakness is often already present, but frequently overlooked until there are other symptoms. People may notice:
- a rounded or ‘dropped’ shoulder
- shoulder blades sticking out (winging)
- thin upper arms
- the eyes remaining slightly open when asleep
- asymmetry in the lips or smile
- difficulty whistling, or drinking from a straw
- difficulty raising an arm above the head
Muscle weakness may progress to affect the ankles and legs; 10-20% of people eventually require a wheelchair. Some people can have mild hearing loss or changes to blood vessels at the back of the eye. Life span is not usually affected except if other conditions such as obesity or severe chest problems add to severe generalised muscle weakness.
FSHD is due to damage from the abnormal switching-on of a gene (DUX4) which is normally turned off in muscle cells. We believe this occurs in FSHD through an unravelling of a normally tightly packed repeated section of DNA on chromosome 4 which includes this gene.
FSHD is diagnosed clinically from the pattern of muscle weakness and family history, and confirmed by testing DNA from blood for the specific repeated section. Most people (90-95%) have FSHD1 with too few repeats, but some have FSHD2 with alteration in a completely separate (chromosome 18) gene (SMCHD1) which influences the DNA packing. Sampling of muscle tissue is not required as muscle cells in FSHD do not show specific features.
There is currently no specific treatment. Regular light exercise is recommended; exhaustive exercise should be avoided. Physiotherapy and posture exercises, ankle splints, and surgery to fix the shoulder blades can all play a role. For the eyes; artificial tears, eyelid surgery, and laser treatment to the retina can be offered. Current research is exploring ways to block or reduce the abnormal stimulation of the DUX4 gene.
For someone with FSHD1, inheritance is autosomal dominant, which means there is a 50% chance that their children will have the condition. In FSHD2 this chance falls between 25 and 50%, as both an SMCHD1 gene alteration and a particular chromosome 4 DNA pattern are required.
Around 10% of FSHD occurs by new alteration in the DNA, particularly in children with the most severe presentation (and almost never in adults with the mildest presentation). A new alteration is often present in some of the cells in one parent of an affected child, despite the parent having no symptoms.
Prenatal testing by chorionic villous sampling at 11 weeks is possible if the DNA alteration in the parent is known. Preimplantation genetic diagnosis in FSHD could be considered in some cases.
FSH-MD Support Group
The Group is a Registered Charity in England No: 205395 and Scotland No: SC039445. It provides information and support to those with FSH-MD and their carers, family and friends.
Group details last updated December 2014.
As facioscapulohumeral muscular dystrophy is a form of muscular dystrophy, advice and information about the condition is also available from the Muscular Dystrophy Campaign (see entry Congenital Muscular Dystrophy).