Keratoconus (KTCN) is a noninflammatory thinning and consequent bulging of the cornea that results in distortion of the corneal surface, altered refractive powers of the eye (both axial and refractive), and reduced visual acuity. In more advanced cases, ... Keratoconus (KTCN) is a noninflammatory thinning and consequent bulging of the cornea that results in distortion of the corneal surface, altered refractive powers of the eye (both axial and refractive), and reduced visual acuity. In more advanced cases, corneal scarring further reduces visual acuity. Symptoms are highly variable and depend on the stage of the progression of the disorder. The trait has an incidence of approximately 1 in 2,000 individuals and is the most common indication for corneal transplantation in the United States (summary by Gajecka et al., 2009). For a discussion of genetic heterogeneity of keratoconus, see KTCN1 (148300).
Gajecka et al. (2009) studied 18 Ecuadoran families segregating autosomal dominant keratoconus without other ocular or systemic features. Family members with KTCN showed conical protrusion of the cornea, prominent corneal nerves, and corneal thinning with or without stromal ... Gajecka et al. (2009) studied 18 Ecuadoran families segregating autosomal dominant keratoconus without other ocular or systemic features. Family members with KTCN showed conical protrusion of the cornea, prominent corneal nerves, and corneal thinning with or without stromal scar tissue. The diagnosis of KTCN was established in 90 individuals who exhibited at least 2 of the following topographic characteristics: curvature of the cornea more than 47 diopters (D) (normal, approximately 43 D); acentric or irregular corneal videokeratography shapes; and/or inferior-superior value differences of 3 D at 3 mm below and 3 mm above the center.
Czugala et al. (2012) analyzed the coding regions and intron-exon junctions of 8 candidate genes in 23 members of an Ecuadoran family (family KTCN-014) with keratoconus mapping to chromosome 13q32, as well as in 2 affected individuals from ... Czugala et al. (2012) analyzed the coding regions and intron-exon junctions of 8 candidate genes in 23 members of an Ecuadoran family (family KTCN-014) with keratoconus mapping to chromosome 13q32, as well as in 2 affected individuals from each of 14 other Ecuadoran KTCN families, all of whom were previously studied by Gajecka et al. (2009). Four variants in 3 genes segregated with disease in family KTCN-014; however, only 1 variant, a Q754H substitution at a highly conserved residue in the DOCK9 gene (607325), was not present in 105 ethnically matched controls, and none of the variants segregated with disease in the other 14 Ecuadoran KTCN families. Czugala et al. (2012) concluded that further studies would be required to assess the contribution of the DOCK9 Q754H variant to familial KTCN.