Fibrosis of Extraocular Muscles with Synergistic Divergence
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
This is usually a congenital condition in which the eyes do not move properly beginning at birth. The lids usually appear to droop (ptosis) as well. Often one eye appears to wink when chewing. The eyes may at times look to the side (diverge). Because the eyes may be fixed in downgaze and the lids droop, patients often have to tilt their heads far back in order to look ahead.
Some individuals with this condition lack the normal amount of skin and eye pigmentation.
Genetics
Inheritance
There have been several reports of parent to child transmission suggesting autosomal dominant inheritance but no specific mutation has been identified.
Pedigree
Autosomal dominant
Autosomal dominant disorders require only one mutation for the disease to be expressed. Since an affected parent has two chromosomes, only one of which has the mutant gene, parents can expect that half (50%) of their children will receive that one and inherit the disease. It is common for individuals that inherit the mutation, however, to not have evidence of the disease (nonpenetrance).
Autosomal dominant inheritance leads to a vertical pattern of transmission
Diagnosis and Prognosis
The diagnosis can be made at birth by a medical eye doctor (ophthalmologist) or a neurologist. Longevity is unlikely to be impacted and vision is normal. In selected individuals surgery on the eye muscles or eyelids can at least partially correct the eye malalignment but it is not possible to restore full motility.
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