Fibrosis of Extraocular Muscles, CFEOM5
Patient Information
Characteristics
Background and History
This is one of several hereditary, nonprogressive forms of strabismus (abnormal alignment of the eyes) in which the eye movements are restricted. Although the name implies a disease of the muscles that move the eye, the primary disorder is one of maldevelopment of the nerves that supply those muscles.
Clinical Correlations
Eyeball movements are severely restricted at birth and they seem to be fixed in their position. In CFEOM5, the eye movements are restricted to some degree in all patients but the nature of the restriction varies. The eyelids may droop (ptosis) severely and can cover part of the pupil. As a result, patients often raise their chin and tilt their heads far back to look ahead. To look around, they have to move their heads. Since blinking is abnormal, the corneas (windshield of the eye) can dry out and this may lead to serious complications. Often one eye becomes lazy (amblyopia) and does not see well.
There are no consistent systemic abnormalities in the rest of the body.
Genetics
Inheritance
CFEOM5 is an autosomal recessive disorder requiring a mutation in both copies of a gene. The parents with a single copy have normal eye movements. However, when such parents have children, each child has a 25% chance of inheriting this eye movement restriction disorder.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
Diagnosis and Prognosis
The diagnosis can be made at birth by an ophthalmologist based on clinical examination of the eyes. A full neurological examination should be done to look for other neurological abnormalities. Surgery can correct the deviation of the eyes although it is usually not possible to restore full movement. Surgery can also correct some of the droopy eyelids. It is important to monitor individuals with this problem to ensure that the cornea receives the proper protective lubrication. The lazy eye should be treated appropriately as well to maintain good vision and, of course, the proper glasses or contacts should be worn for the best vision.
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