Anterior Segment Mesenchymal Dysgenesis
Patient Information
Characteristics
Background and History
This is another example of a mutation in a gene regulating the formation of embryonic tissue with serious consequences in subsequent development. In this case the tissues involved are primarily the cornea (windshield of the eye) and the lens.
Clinical Correlations
Infants are born with deformities of the cornea and iris. This can be mild or severe enough to cause dense cloudiness. The iris may be partially adherent to the cornea which is often smaller than normal. The lens usually has some opacities. These may be mild but are often progressive. Other patients have dense opacification of the lens from birth. Vision is highly variable, ranging from normal to bare motion detection. Glaucoma is usually not a clinical feature and there are no systemic abnormalities.
Genetics
Inheritance
Mutations in at least 2 genes seem to be responsible for this disorder which is inherited in an autosomal dominant pattern. Parents with this condition have a risk of 50% of passing the mutation to each of their children.
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
This condition is diagnosed by an ophthalmologist who does a complete eye examination to determine the extent of the abnormalities. Cataracts sufficiently dense to interfere with vision can be surgically removed. Corneal transplantation has been done in patients who have severe opacification.
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