What is FSHD?
This is a condition that causes weakness of the facial muscles (facio), the muscles around the shoulder blade (scapulo) and upper arm muscles (humeral). It was originally called Landouzy-Dejerine syndrome after the two French doctors that initially described the condition in 1884. It is thought to affect anywhere between 1 in 8,500 and 1 in 25,000 people.
What causes FSHD?
FSHD is a genetic condition that an individual is born with. The genetic variance is inherited in an autosomal dominant manner, meaning that the off-spring of an affected parent have a 50% chance of also developing FSHD. In addition to inheriting the condition, 10-30% of cases occur after a spontaneous change in the genetic make-up of an individual during fetal development and result in FSHD. This would mean an individual having the condition without either parent being affected.
There are two main types of FSHD: FSHD1 affects 95% of patients and FSHD2 affects the remaining 5% of patients. In both cases the genetic DNA code affected lies on chromosome 4 and is referred to as the D4Z4 region. The D4Z4 region can be considered as a control centre on chromosome 4 and is responsible for suppressing the genes local to it. In FSHD, the D4Z4 area doesn’t function properly and results in the increased activity of genes that would normally be silent. The decreased activity in the D4Z4 area can be because it is shorter than normal (FSHD1) or there being lack of activity in another gene (SMCHD1) that would normally activate D4Z4 (FSHD2). In both cases, with the D4Z4 area being underactive, there is subsequent over activity of a neighbouring gene called DUX4. It is the increased activity in the DUX4 gene that is thought to result in damage to the muscle cells resulting in muscle wasting and weakness.
What are the symptoms of FSHD?
The symptoms are usually evident by 20 years of age, but may begin to show in childhood. 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 blades)
- Upper arm muscle weakness (Loss of muscle bulk in upper arms, difficulty bending elbow)
It can also cause weakness of muscles elsewhere in the body, with 20% of affected individuals losing the ability to walk. The major complication of the condition occurs with weakness developing in the muscles involved with breathing, as this predisposes the patient to chest infections and the need for artificial ventilation. This complication can occur in around 1% of affected individuals. In the majority of individuals, however, the life expectancy is unchanged from unaffected individuals.
How is FSHD diagnosed?
The most accurate method of diagnosis involves genetic testing via a blood test. Currently the only laboratory performing the genetic analysis is based in Bristol and it can take many weeks or months for the results to come back. In addition, blood tests looking for muscle damage (raised creatine kinase), tests that look at the activity of the muscle when stimulated (electromyography) and muscle biopsies are performed.
What are the treatments for FSHD?
There is currently no cure for FSHD, although increasing knowledge of the genetics causing the condition will help scientists develop medications to target the affected genes.
Currently a combination of physiotherapy and occupational therapy are the mainstay of treatment to ensure that joint mobility/strength and independent activity are maintained wherever possible. It would be recommended that a specialist neurologist and therapist review the patient around once per year. At these review appointments the specialists can check the patient’s progress and teach new exercises and coping methods to best improve the level of function.
The use of medications, such as albuterol, to increase muscle mass have been tried although the increased muscle mass has not been shown to improve movement and strength. Surgery can be performed to fix the shoulder blade to the rib cage to improve the strength around the shoulder, but consultation with an orthopaedic surgeon would be required to discuss this further.
http://ghr.nlm.nih.gov/condition/facioscapulohumeral-muscular-dystrophy. Detailed information about the genetics of FSHD.
Last reviewed: 13-08-2019 || Next review due: 13-08-2022