Ring Dermoid Of Cornea

A number sign (#) is used with this entry because of evidence that ring dermoid of the cornea can be caused by heterozygous mutation in the PITX2 gene (601542) on chromosome 4q25.

Clinical Features

Mattos et al. (1980) reported a Peruvian family in which the grandmother, all 3 of her children (daughters), and 1 of the 2 sons of a daughter had bilateral annular limbal dermoids with corneal and conjunctival extensions. There were no associated extraocular anomalies. The choristomas (mass of tissue histologically normal for another site) involved the limbus for 360 degrees, and extended anteriorly onto the cornea and posteriorly about 5 mm. (Conjunctival and limbal dermoids occur with the Goldenhar syndrome (164210).) Each patient had hairs growing from the tumor mass.

Xia et al. (2004) studied a large Chinese family in which 21 individuals were affected by RDC. Patients showed yellow-white tumor-like apophyses on the corneal border of both eyes. The apophyses were clinically detectable at birth and progressively impaired the patients' vision with aging. Some affected individuals also had glaucoma, unilateral cataracts, or involuntary oscillation of the eyes. The only clinical manifestation in the affected individuals was in the eyes. Affected cases were found in both males and females in each of 4 generations, with instances of male-to-male transmission.

Mapping

In a large Chinese family segregating RDC, Xia et al. (2004) found linkage of the disorder to chromosome 4q24-q26.

Molecular Genetics

In affected members of a large Chinese family segregating RDC, Xia et al. (2004) identified heterozygosity for an R62H mutation in the PITX2 gene (601542.0012); the mutation was not found in 8 unaffected members of the family.