Sir,

Ring chromosome 17 was first described in 1970. There have been 4 previous reports of flecked retina associated with ring chromosome. We report another case of ring chromosome 17 with flecked retina.

Case report

We present a 25-year-old boy, who presented 23 years ago with myoclonic seizure, learning disability, and developmental delay. There were no signs of dysmorphism or any skin lesions. CT scan of the head showed no definite abnormalities. No family history of seizures or visual problems were reported.

Ocular examination at the age of 16 years revealed VA of 6/6 in both eyes. Low-frequency jerk nystagmus was apparent on dextroversion. Fundoscopy revealed well-defined white foveal flecks at the level of retinal pigment epithelium in both eyes (Figure 1).

Figure 1
figure 1

Fundus photographs of reported patient showing well-defined white foveal flecks at the level of the retinal pigment epithelium.

Full size image

Karyotype analysis (Figure 2) showed 46 XY, r(17)(p13.3q25) with no obvious loss of genetic material. Fluorescence in situ hybridisation studies (Figure 2) using the Oncor D17s379 probe from the Miller–Dieker chromosome region on 17p13.3, revealed no deletion. Probes within 300 kb of each telomere showed signals on normal chromosome 17 only, suggesting that at least 300 kb of material has been lost from each arm.

Figure 2
figure 2

Karyotypic analysis showing ring chromosome 17. (a) G-banded karyotype showing ring chromosome 17 (arrowed). (b) Fuorescence in situ hybridisation with probes from 17q21 (RARA) and 17p13.3 (Oncor D17s379, Miller Dieker region) showed that both probes are present on ring chromosome. This confirms that there is loss of little chromosome material from the P arm of chromosome 17. (c) Ideogram of the ring 17 chromosome.

Full size image

No abnormality in parental chromosome confirmed this as a de novo change.

Comment

Four other cases of flecked retina associated with ring 17 chromosome have been reported.1, 2, 3, 4 The reported cases were associated with short stature, mental retardation, epilepsy, and café-au-lait spots. Neurofibromotosis can be misdiagnosed in these cases due to the presence of café-au-lait spots. Fundus fluorescein angiogram showed normal retinal and choroidal vascular filling.1, 2, 3, 4

Retinal spots or flecks are seen in a range of heritable ocular disorders, including age-related macular degeneration, pattern dystrophy, Stargardt disease, fundus flavimaculatus, Bietti's crystalline dystrophy, as well as being part of multisystemic phenotypes, such as Alport disease, primary hyperoxaluria, and Gaucher disease. Such flecks may be caused by an isolated abnormality of receptor or RPE metabolism leading to the accumulation of abnormal material within the RPE or Bruch's membrane.2, 3 Retinal flecks have also been reported in cases of ring chromosome 14.5 This may be a non-specific consequence of ring chromosome formation. However, it remains possible that loci on chromosome 17 may be involved in the regulation of RPE or photoreceptor function. Future detailed mapping of the chromosomal imbalance in such patients will be critical in defining whether this is the case.