Bietti's crystalline corneoretinal dystrophy: a cross-sectional study.

To evaluate the prevalence of Bietti's corneoretinal dystrophy (BCD) in a reference population of retinitis pigmentosa (RP), and to document the disease course clinically and angiographically by a cross-sectional approach. Two hundred seven consecutive RP patients were ascertained within a 3-year period. All patients had a complete eye examination, including fluorescein and indocyanine green angiography (FA, ICG). Blood samples were collected for electron microscopy evaluation of circulating lymphocytes of BCD patients. Six patients were diagnosed with BCD. Prevalence was 3% of nonsyndromic RP cases. Limbal corneal and intraretinal crystals were found in all cases. In the early phase of BCD, ICG revealed focal lobular areas of choriocapillary atrophy at the equator, with concomitant retinal pigment epithelium (RPE) changes at the posterior pole on FA. These lesions gradually progressed both anteriorly and posteriorly, sparing an incomplete peripapillary ring and macular island until late in the disease. Progressive sclerosis of ciliary and choroidal arteries was noted upon ICG. The presence of lysosomal crystals was documented in a subpopulation of circulating lymphocytes that seemed to increase with age. The present study is the first to assess BCD prevalence in a population of retinitis pigmentosa patients, to describe clinically and angiographically its evolution from first symptom to legal blindness, and to localize the first fundus alterations not only at the posterior pole but also at the equator.