Genetics of Cataract

Abstract Cataract affects all ages, sexes, and populations. Mendelian cataract is usually of early onset, with or without a family history. The term “congenital/infantile cataract” refers to lens opacities that present at birth or are detected in the first year of life. This condition is one of the most common preventable causes of childhood blindness globally. In developed countries congenital cataract is often genetically determined, with an approximate incidence of 30 cases for every 100,000 births. Inherited cataract is most often bilateral and “isolated,” although an association with other ocular and systemic abnormalities (as seen in developmental and chromosomal defects) is not uncommon. It is important to suspect a potential systemic component, as this may lead to prevention of comorbidities. According to OMIM (Online Mendelian Inheritance in Man, cataract appears in 899 “hits,” which include numerous syndromes. Genetically determined cataract is often autosomal dominant worldwide, although autosomal and X-linked recessive inheritance patterns occur. This chapter discusses the genetics of cataract. Other causes of congenital cataract include prenatal exposure to rubella among other infectious cause (e.g. syphilis, toxoplasmosis); rubella accounts for most congenital cataract in certain developing countries. Other types of acquired cataract include trauma and drugs and will not be discussed herein. Age-related cataract is more of a complex trait for which the genetic background is being deciphered.