Sir,

Renal-coloboma syndrome (RCS) is an autosomal dominant disorder caused by PAX2 gene mutations and defined by the association of optic nerve coloboma and renal hypoplasia.1, 2, 3 We report a previously unknown phenotypic presentation of RCS in which calcified keratopathy and posterior lens luxation were associated with optic nerve defect.

Case description

A 10-year-old girl was referred to our hospital because of progressive loss of visual acuity in the right eye. Several years before, the child had been diagnosed as having RCS on the basis of renal hypoplasia associated with optic nerve colobomas. Genetic studies had confirmed the presence of a heterozygous PAX2 gene mutation: 619insG. The child had additional anomalies such as mental retardation, epilepsy, vesicoureteral reflux, and joint laxity. There was no history of ocular trauma, and no family history of renal or ocular disorder was identified. Examination under anaesthesia revealed severe calcified keratopathy of the right cornea (Figure 1). The lens did not seem to be present through the pupil of the right eye and fundus was hardly accessible because of corneal opacity, so that a B-scan ultrasonography was performed and showed posterior lens luxation (Figure 1). As expected, the left eye fundus revealed an optic disc coloboma.

Figure 1
figure 1

Unusual ocular phenotype associated with RCS and PAX2 mutation (a–d). Operating room photographs of right eye (a) and left eye (b). The right cornea presented with severe calcified keratopathy (a) whereas the left anterior segment appeared normal (b). (c) B-scan ultrasonography of the right eye showing lens dislocation (asterisk) in the vitreous and optic nerve colobomas (white arrow). on: optic nerve. (d) Photograph of left eye fundus showing optic disc coloboma.

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Comment

In this case report, the extra-ocular phenotype is characteristic of RCS. Conversely, the phenotype exhibited on the right eye has not been previously reported. Calcified keratopathy, which represents the first corneal defect ever documented in RCS, is probably consecutive to chronic renal failure with calcium phosphate disturbances.4 The second intriguing ocular abnormality was the presence of spontaneous lens luxation. Interestingly, investigators have previously reported that patients with RCS may have joint abnormalities such as joint laxity.2, 5 In this case, the child also suffered from joint laxity and had been operated on for bilateral hip dislocation. Therefore, we suggest the possibility that lens luxation could be part of a general disorder involving the connective tissue or elastic fibres of different types and locations. This original description stresses the importance of investigating potential cornea or lens damage in patients presenting with such a syndrome.