What is Facioscapulohumeral Muscular Dystrophy?
Facioscapulohumeral Muscular Dystrophy is a neuromuscular condition characterized by gradual progressive muscle atrophy and weakness.1 The muscles which are mainly affected by this condition are the facial muscles, muscles of the shoulder blades, and the muscles of the upper arm.
In some cases, even the lower extremity muscles like the muscles of the trunk and the hamstring muscles are also affected by Facioscapulohumeral Muscular Dystrophy. This is a congenital condition meaning that a child is born with this condition but the symptoms are apparent by the time the child is about 20 years of age even though in some cases the symptoms may be seen in early infancy and childhood.
The severity of the symptoms of Facioscapulohumeral Muscular Dystrophy are extremely variable in that while some individuals may be severely debilitated by the condition there are others who may remain completely asymptomatic despite having Facioscapulohumeral Muscular Dystrophy.
This condition progresses extremely slowly and there is no affect on the life expectancy of the affected individual as a result of Facioscapulohumeral Muscular Dystrophy. This condition follows an autosomal dominant pattern of inheritance meaning that one copy of the faulty gene from any parent is good enough for an individual to develop Facioscapulohumeral Muscular Dystrophy.
What are the Causes of Facioscapulohumeral Muscular Dystrophy?
Facioscapulohumeral Muscular Dystrophy has two subdivisions type I and type II. The root cause for the development of Facioscapulohumeral Muscular Dystrophy type I is a defect in the DUX4 gene. This gene is located in the D4Z4 region of chromosome 4.2
This region of the chromosome has excessive methyl groups but in cases of Facioscapulohumeral Muscular Dystrophy type I the number of methyl groups is significantly less in numbers resulting in the DUX4 gene to produce the DUX4 protein in cells and tissues where they are not normally produced which in turn causes the muscle atrophy and weakness associated with Facioscapulohumeral Muscular Dystrophy type I.
This condition follows an autosomal dominant pattern of inheritance meaning that one copy of the faulty gene from either parent is good enough for a child to develop Facioscapulohumeral Muscular Dystrophy type I.
Facioscapulohumeral Muscular Dystrophy type II is also an autosomal dominant inherited condition but in this cases the mutation is in the SMCHD1 gene which decreases the methyl groups in the 4Z4 region of chromosome 4 thus causing the DUX4 gene to produce proteins in areas where DUX4 gene is not produced resulting in the progressive muscle weakness and atrophy seen in Facioscapulohumeral Muscular Dystrophy type II.
What are the Symptoms of Facioscapulohumeral Muscular Dystrophy?
Progressive muscle weakness and atrophy in the facial muscles, the muscles of the shoulder blades, and the upper arm muscles are the primary features of Facioscapulohumeral Muscular Dystrophy.
As a result of the facial weakness, there will be restricted movements of the lips causing difficulty with chewing, trying to whistle or using a straw. The affected individual will also have masked like facies.
Improper closing of the eyes is also another feature of Facioscapulohumeral Muscular Dystrophy as a result of facial weakness. The weakness of the muscles of the shoulder blades may in turn cause weakness of the muscles of the neck and the muscles of the upper arm which may cause decreased ability to flex and rotate the shoulder, shoulder instability, and scapular winging which is the most common finding in individuals with Facioscapulohumeral Muscular Dystrophy.
The scapular winging becomes prominent as the affected individual tends to raise the arm to the side. Affected individuals also have an inability to raise their arms overhead or even at the shoulder levels due to muscle weakness.
Facioscapulohumeral Muscular Dystrophy may also affect other muscles of the body to include the abdominal wall, the hip, and the thigh muscles. Affected individual also will tend to have an abnormal gait pattern with a Trendelenburg pattern of gait.
As a result of weakness of the lower extremities and foot there may be resultant footdrop. Kyphoscoliosis and lordosis are also something which can be seen in individuals with Facioscapulohumeral Muscular Dystrophy. In some cases, visual and hearing deficits are also seen in individuals with Facioscapulohumeral Muscular Dystrophy.
How is Facioscapulohumeral Muscular Dystrophy Diagnosed?
A thorough clinical evaluation and a detailed history of the patient may help in coming to a diagnosis of Facioscapulohumeral Muscular Dystrophy, in particular if there is a family history with a family member having this condition.
A blood test may reveal elevated levels of creatine kinase which may also point towards a diagnosis of Facioscapulohumeral Muscular Dystrophy. The most recommended test for diagnosing Facioscapulohumeral Muscular Dystrophy is an EMG of the upper and lower extremities along with nerve conduction tests which will clearly show weakness of the muscles which is a classic sign for this condition.
Additionally a muscle biopsy of the affected muscle may also confirm the diagnosis of Facioscapulohumeral Muscular Dystrophy. Genetic testing may be done which will show abnormalities in the DUX4 and SMCHD1 gene confirming the diagnosis of Facioscapulohumeral Muscular Dystrophy.
How is Facioscapulohumeral Muscular Dystrophy Treated?
The treatment for Facioscapulohumeral Muscular Dystrophy is symptomatic. It requires a coordinated effort from a variety of specialists to include pediatricians, neurosurgeons, neurologists, physical therapists, and occupational therapists.
Aggressive physical therapy is recommended to increase the muscle strength and tone and decrease the atrophy of the muscle caused by Facioscapulohumeral Muscular Dystrophy.
For gait abnormalities, aids may be provided to the patient to help him or her ambulate more normally. Orthotics is also of great help in normalizing the ambulatory function of the affected individual. In some cases as a result of severe weakness the patient may no longer be able to ambulate independently and may require use of a wheelchair.
For other impairments like hearing deficits, hearing aids may be of great help in patient with Facioscapulohumeral Muscular Dystrophy. In some cases surgery may have to be done where the shoulder blades are attached to the chest wall to stabilize the scapular structures and increase movement of the arms which becomes severely restricted as a result of this condition.
