Ectopia lentis is a zonular disease characterized by the subluxation of the lens resulting from the disruption of the zonular fibers. Patients with ectopia lentis commonly present with a marked loss in visual acuity that varies with the degree of lens subluxation in addition to a number of possibly accompanying ocular complications including cataract, myopia, retinal detachment, and glaucoma.
Genetic heterogeneity is observed in Isolated ectopia lentis. Mutations in the ADAMTSL4 gene are found to be responsible for autosomal recessive isolated ectopia lentis-2 (ECTOL2), whereas autosomal recessive isolated ectopia lentis-1 (ECTOL2) is caused by mutations in the FBN1 gene.
[See: Jordan > Al-Salem, 1990].
Al-Salem (1990) described two large consanguineous Arab families of Iraqi and Jordanian origin, respectively, with bilateral isolated ectopia lentis. The condition was generally discovered at school age (5-6 years). All patients in both families had normal clear corneas and deep anterior chambers with tremulous irides. There were no areas of iris atrophy, pupillary abnormalities, or iris transillumination in any of the 18 patients examined or their relatives. The subluxated lenses showed variation in their direction from one patient to another, but temporal displacement was the most common direction encountered. Refraction showed myopic astigmatism; all patients had normal intraocular pressures and axial lengths. Systemic examination revealed no arachnodactyly, joint hyperextensibility, scoliosis, or cardiac anomalies, and span-to-height measurements were normal in all patients.
Ahram et al. (2009) studied one of the families of Al-Salem (1990). The consanguineous Arab family of Jordanian origin consisted of 15 affected individuals from four related sibships with autosomal recessive isolated ectopia lentis. Ahram et al. (2009) mapped the ectopia lentis locus in this family to the pericentromeric region on chromosome 1 (1p13.2-q21.1). The diagnosis was based on ocular involvement without systemic manifestations. In all examined affected individuals, the corneas were clear, pupils were round and normal, and there were no areas of iris atrophy or positive iris transillumination. The displacement of the lens was variable among the examined affected individuals. This family showed variable degrees of lens displacement among affected members with deprivation amblyopia, retinal detatchment and cataract but no manifestations in any other system. Mutation screening of four candidate genes revealed a homozygous nonsense mutation in exon 11 of ADAMTSL4 (p.Y595X; c.1785T>G) in all affected individuals that is absent in 380 control chromosomes. The mutation was found to be segregated with the phenotype in the family. Ahram et al. (2009) concluded that mutations in ADAMTSL4 are responsible for autosomal-recessive simple ectopia lentis and that ADAMTS-like4 plays a role in the development and/or integrity of the zonular fibers.
[See also: Jordan > Al Salem, 1990; Ahram et al., 2009].