Monday, February 12, 2007

Section 11-A: Genetic basis of glaucoma.

Several lines of evidence indicate that glaucoma has a genetic basis, that is, glaucoma is caused in part by defects in specific genes (Table 11-1). First, although many cases of glaucoma occur with no family history of disease, glaucoma appears to be clearly heritable in some families. A number of large families have been reported in which glaucoma is inherited as a simple Mendelian trait (usually with autosomal dominant inheritance). Studies of the epidemiology of glaucoma also support the notion that there is a significant genetic component. Relatives of individuals affected with glaucoma have a much higher risk of developing glaucoma when compared to the general public. Additionally, many of the individual signs of glaucoma are heritable themselves, including cup to disc ratio and IOP. When these key features of glaucoma are examined individually, they appear to run in families. Lastly, the frequency of glaucoma varies greatly between different ethnic and racial groups. For example, the prevalence of glaucoma in African Americans is significantly higher than that of whites, which suggests that African Americans have a higher risk of developing glaucoma due to a heritable factor that is more prevalent in this racial group.

Table 11-1. Evidence that glaucoma is caused at least in part by genes.

Evidence that glaucoma has a genetic basis

Families that show clear inheritance of glaucoma

Relatives of glaucoma patients have a higher rate of developing glaucoma themselves

Features of glaucoma (large cup to disc ratio and high intraocular pressure) are heritable

Glaucoma is more common in some ethnic and racial groups than others

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