Cataracts, Congenital, Autosomal Dominant
Patient Information
Characteristics
Background and History
The lens of the eye functions as any optical lens, i.e., to focus light. To do that, it must be clear and of the proper size and curvature to focus images clearly on the retina, which then sends them to the brain. Cataracts, or opacifications of the lens, have been known since antiquity. They may form in utero, during the neonatal period, and in young and old people. The majority occur as part of the aging process in which case they are known as age-related cataracts. They may also result from trauma, metabolic disease, infections, and gene mutations. Here we discuss only inherited cataracts that are transmitted directly from one generation to the next.
Clinical Correlations
Any opacity in the lens is called a cataract. Such opacities can be of various sizes, shapes, color, and location. These are not always visually significant and are often congenital in origin. However, many do interfere with proper focusing of images in which cases vision is blurry, sometimes significantly.
Cataracts may occur in one eye or both. There is often considerable variation in their appearance even among the two eyes, or among family members. Many lens opacities progressively enlarge or become denser while others are stable.
Genetics
Inheritance
Here we consider only cataracts that result from gene mutations and are inherited in an autosomal dominant pattern. Affected parents transmit their gene mutation directly to their children with the result that the transmission appears vertical in the family tree. However, the cataracts are highly variable in morphology among family members.
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
Cataracts can be diagnosed in their advanced state when the pupil of the eye is white. However, an ophthalmologist requires a complete eye examination to ensure that other conditions such as glaucoma are not present and to determine the nature and density of the lens opacity. In autosomal dominant cataracts there are no associated systemic abnormalities.
Most cataracts by themselves do not cause other eye problems. Their primary impact is on vision but small opacities may not cause any noticeable degradation in seeing and the lens does not necessarily need to be removed. Cataract surgery is a highly technical procedure and like any surgery has some risks. However, the majority of patients do well postoperatively and achieve a good visual result. Your eye doctor can help you decide if surgery is required.
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