Sir,

Tapetoretinal degeneration with crystals at the corneal limbus, numerous yellow, glistening retinal deposits, and progressive atrophy of the retinal pigment epithelium (RPE) and choroid was reported by Bietti in 1937.1 The corneal deposits are detected in only about one-third of patients, and when corneal changes are absent, the term ‘Bietti crystalline retinopathy’ is used.2, 3 The inheritance is autosomal recessive and mutations in CYP4V2 gene on chromosome 4q35 has been associated with Bietti crystalline retinal dystrophy.4

Central visual loss usually occurs in the later stages of the disease due to RPE and choroidal atrophy.

Choroidal neovascularization (CNV) may be seen with any pathological process disturbing the RPE and Bruch's membrane. However, to the best of our knowledge, CNV has not been reported in Bietti crystalline retinal dystrophy. Here, we report a case of peripapillary CNV with serous retinal detachment in Bietti crystalline retinal dystrophy.

Case report

A 13-year-old girl was referred to our institution for further evaluation of a presumed retinal dystrophy. Her past medical and family histories were unremarkable. She did not have any visual complaints. Visual acuity was 20/20 and anterior segment examination was normal in both eyes. However, fundus examination revealed bilateral numerous yellowish, glistening intraretinal crystals distributed throughout the posterior pole and peripapillary RPE atrophy (Figure 1a). Visual field examination was normal with Humphrey 30-2 standard automated perimetry.5 Electrophysiological tests were performed within the limits of ISCEV standards6, 7 and electroretinography showed normal photopic and scotopic responses. Electro-oculography was also normal, with an Arden ratio of 2.08 OD and 2.06 OS. The patient was diagnosed with Bietti crystalline retinal dystrophy on a clinical basis and it was not possible to confirm the diagnosis by molecular analysis. After 14 months, she came for urgent re-evaluation because of a sudden decrease in vision to 20/50 in her left eye. Fundus examination revealed exudation with localized retinal detachment at the temporal side of the optic disc extending to the fovea (Figure 1b). There was no autofluorescence of the disc, and fluorescein angiogram demonstrated a rather poorly defined hyperfluorescent peripapillary membrane with a hypo- and hyperfluorescent spots at the posterior pole in the early stages and leakage from the peripapillary membrane in the late stages (Figure 1c). The indocyanine green angiogram (ICGA) showed a hypofluorescent peripapillary membrane with hypofluorescent spots at the posterior pole in the early stages and a hyperfluorescent peripapillary membrane with hypo- and hyperfluorescent spots at the posterior pole in the late stages (Figure 1d). Optical coherence tomography revealed a sensory retinal detachment and serous retinal pigment epithelial detachment extending from the optic disc to the fovea (Figure 2a and b).

Figure 1
figure 1

(a) Fundus photography of left eye at first examination revealing intraretinal crystals scattered throughout posterior pole. (b) Fundus photography of left eye 14 months after first examination. Exudation with localized retinal detachment at temporal side of optic disc extending to fovea is seen. (c) Late stage fluorescein angiogram demonstrating poorly defined hyperfluorescent peripapillary membrane with leakage and hypo- and hyperfluorescent spots at posterior pole. (d) ICGA showing hyperfluorescent peripapillary membrane with hypo- and hyperfluorescent spots.

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Figure 2
figure 2

The optical coherence tomography revealed sensory retinal detachment and serous retinal pigment epithelial detachment extending from optic disc to fovea. (a) Nasal-to-temporal, (b) superior-to-inferior.

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Comment

It has been reported that visual acuity is relatively good during the early stages of Bietti crystalline retinopathy with subsequent progressive but rather slow visual loss over decades due to chorioretinal atrophy.8 In our case, central vision deteriorated rapidly due to extension of exudation of peripapillary CNV to the fovea. The mechanism of CNV formation in our case is unclear; however, RPE and choroidal atrophy may have played a role.

In this case, ICGA showed hypofluorescent spots at the posterior pole in the early stages and hypo- and hyperfluorescent spots in the late stages. These findings could be explained by the study of Salati et al,9 where early phase ICGA revealed focal lobular areas of choriocapillary atrophy at the equator, with concomitant RPE changes at the posterior pole on FA in a patient with Bietti crystalline retinopathy. Progressive sclerosis of ciliary and choroidal arteries was also noted on ICGA.

In conclusion, CNV can occur in Bietti crystalline retinal dystrophy. Therefore, in patients with Bietti crystalline retinal dystrophy and rapid visual loss, CNV should be suspected.

The authors have no financial or commercial interest related to this study. No public or financial support used for this study.