Ehlers-Danlos syndrome, known as EDS, is the name given to a group of 13 related genetic disorders that affect the connective tissue. The symptoms of many of the EDS types overlap, but each type has distinctive features that help doctors with the diagnosis.
In musculocontractural EDS or mcEDS, also sometimes called adducted thumb and clubfoot syndrome, patients are born with adducted thumbs — where the thumb is twisted so it lies across the palm — and clubfoot.
mcEDS is very rare, thought to affect less than 1 in a million people worldwide.
What causes mcEDS?
mcEDS is caused by mutations in the CHST14 gene. That gene contains the information necessary for cells to make an enzyme involved in producing an important structural component of the extracellular matrix — the scaffold and anchoring points for cells to form tissues. Defects in this enzyme lead to these anchor points being weak and not being recognized by structural proteins, which results in the symptoms of mcEDS.
How is mcEDS inherited?
mcEDS is inherited in an autosomal recessive pattern, meaning that a child must inherit two faulty copies of the CHST14 gene — one from each parent — to develop the disease. Parents with only one copy of the faulty gene are carriers of mcEDS and likely have no symptoms.
If both parents are carriers of mcEDS, their children have a 1 in 4 chance of inheriting two copies of the disease-causing mutation and developing mcEDS. Such children have a 1 in 2 chance of inheriting only one copy of the disease-causing mutation and being carriers like their parents. The chances are 1 in 4 that these children will only inherit the healthy copies of the gene, which would result in them neither developing the disease nor being carriers.
What are the symptoms of mcEDS?
In addition to adducted thumbs and clubfoot, people with mcEDS have long, spidery fingers. Some patients are born with a cleft palate, and abnormalities in the heart, kidneys, and intestines. Delayed development and weak muscle tone (hypotonia) may be evident in infancy. Cognitive development is normal.
How is mcEDS diagnosed?
mcEDS is diagnosed based on a physical examination and the patient’s family history. The major criteria for the initial diagnosis are adducted thumb and clubfoot at birth.
To confirm a diagnosis of mcEDS, the physician will order a genetic test. A small sample of blood will be drawn from the patient and sent to a laboratory to be examined for any mutations in the CHST14 gene. The results of the test may take four to six weeks to become available. Based on the results, the doctor may ask for additional tests to check for any complications that are common in mcEDS, including heart abnormalities.
How is mcEDS treated?
There currently is no cure for mcEDS or the other types of EDS. However, there are treatments available to manage some of the symptoms. Physiotherapy can help strengthen muscles. Surgery may be necessary to correct thumb adduction and clubfoot.
Last updated: Nov. 5, 2019
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