Keratoconus (KTCN, OMIM 148300) is a thinning and anterior protrusion of the cornea that results in altered refractive powers and loss of visual acuity. The prevalence of the disease is estimated to be 1:2000 in the general population.
1 Although most diagnosed KTCN cases are sporadic, patients with positive family history are also observed.
2 The frequency of familial KTCN is ranged between 6% and 26% of KTCN cases.
3–5 Despite numerous studies, the reasons of development and progression of this disorder remain elusive. Genetic studies of KTCN families have led to identification of several significant and suggestive loci linked with KTCN.
2 To date, only one locus, 5q21.2, has been described in two different populations.
6,7 Although the majority of genetic studies were performed for familial forms of KTCN, unrelated individuals with KTCN were also examined in single-gene analyses
8 and whole-genome studies.
9,10 One of the most widely studied genes in KTCN etiology is
VSX1. Mutations in
VSX1 have been described as related to the KTCN phenotype.
11–13 However, numerous studies, have not confirmed these findings.
14–17 The second candidate gene analyzed in KTCN is
SOD1. Although some disease-causing mutations in
SOD1 have been indicated as related with KTCN,
18 this relationship has not been confirmed in other populations.
15,19,20