SNP Shot: Genomic Insights

Peters anomaly is an eye condition affecting the anterior segment, the front part of the eye. This area includes the lens, iris (the colored part), and cornea (the clear outer covering). Normally, these structures develop separately. However, in Peters anomaly, the anterior segment's development is flawed, resulting in incomplete separation between the cornea and either the iris or the lens. This leads to a cloudy (opaque) cornea, which impairs vision. The size and density of the corneal opacity varies, ranging from slight streaks to large, dense white areas. The location of the clouding also differs; it may be central or off-center. Central, large opacities generally cause more significant vision problems compared to smaller, peripheral ones.

Approximately half of those with Peters anomaly experience low vision early in life, and about 25% are legally blind. Some individuals may develop amblyopia (lazy eye) due to reduced visual stimulation. Peters anomaly is often linked to other eye conditions like glaucoma (increased eye pressure), cataracts (clouding of the lens), and microphthalmia (unusually small eyes). In most instances, Peters anomaly is bilateral, affecting both eyes, although the severity of vision loss may differ between the eyes. Strabismus (misaligned eyes) may also be present. In some cases, corneal clouding can improve over time, leading to better vision.

There are two types of Peters anomaly, distinguished by their characteristics. Type I involves incomplete separation of the cornea and iris with mild to moderate corneal clouding. Type II involves incomplete separation of the cornea and lens with severe corneal clouding, potentially affecting the entire cornea.

Inheritance:

Most Peters anomaly cases are sporadic, meaning they occur in individuals with no family history of the condition. In many sporadic cases, the underlying genetic cause remains unknown. However, some sporadic cases are caused by a new gene mutation or by inheriting a mutation from unaffected parents. Rarely, the condition (or related eye disorders) has been reported in multiple family members. Whether the case is sporadic or inherited, when Peters anomaly is caused by a mutation in the CYP1B1 gene, it is inherited in an autosomal recessive manner. This means that both copies of the gene in each cell must have mutations for the condition to develop. The parents each carry one copy of the mutated gene, but typically do not show signs and symptoms of the condition. When caused by mutations in the FOXC1, PAX6, or PITX2 genes, the condition follows an autosomal dominant inheritance pattern. In this case, only one copy of the altered gene in each cell is sufficient to cause the disorder.