Autofluorescence of choroidal vessels in Bietti’s crystalline dystrophy

Abstract

ObjectiveTo describe the pattern of fundus autofluorescence (FAF) in Bietti’s crystalline dystrophy (BCD).Methods and analysisFrom the National Institutes of Health EyeGene database of 2769 patients with known pathogenic mutations, 5 patients with BCD-causing CYP4V2 mutations who had FAF images were selected. Demographic and genetic information and imaging files were obtained. From the FAF imaging files, unique autofluorescence (AF) patterns and correlation with retinal structures were assessed by three investigators for clinical significance.ResultsFive patients (four males, one female; mean age 56 years, range 42–76 years) were included, all with different CYP4V2 mutations. All patients displayed varying degrees of hypo-AF in the posterior pole. In four out of five patients, there was a relative hyper-AF of choroidal vessels within the hypo-AF area; this feature was limited to sclerotic vessels only. A transitional zone of speckled AF was visible around the hypo-AF area. This zone corresponded to the area containing retinal crystals on colour fundus photography; however, retinal crystals did not demonstrate hyper or hypo-AF.ConclusionsThis study presents a previously unreported characteristic finding in patients with BCD with CYP4V2 mutations. AF of choroidal vessels may aid in differentiating BCD from other retinal dystrophies.

An In-Depth Single-Gene Worldwide Carrier Frequency and Genetic Prevalence Analysis of CYP4V2 as the Cause of Bietti Crystalline Dystrophy

“…Although often used in diagnosing BCD, retinal crystals are not unique to BCD 29 and may not be visible in early or late disease stages. 30 , 31 Near-infrared imaging can enhance detection of retinal crystals and improve correct diagnosis. 20 , 32 , 33 Therefore, there is in low awareness of BCD among ophthalmologists, and genetic testing for CYP4V2 mutations is the ultimate tool to confirm BCD diagnosis.…”

Fundus Autofluorescence and Clinical Applications

“…[188] This eventually leads to diffuse hypo-AF with remaining isoAF irregular islands of RPE. However, hypo-AF and hyper-AF lesions are not spatially correlated with the crystalline deposits on color imaging, [189,190] and NIR-R appears to visualize the crystalline deposits best, although this is also variable. [191] Sclerotic choroidal vessels are typical in BCD and underlie regions of chorioretinal atrophy that can be seen on color imaging.…”

“…These sclerotic vessels have been shown to be hyper-AF on SW-AF, while non-sclerotic choroidal vessels remain hypo-AF. [190] Mutations in the CRB1 gene can lead to both LCA and RP with distinctive FAF features. Typical findings of peripheral bone-spicule retinal and RPE degeneration with or without hyper-AF macular rings can be found.…”

A patient advocating for transparent science in rare disease research

“…BCD patients have numerous tiny, shiny yellow-white retinal crystals (Fig. 1D), though crystals may disappear in late disease stage [11,13,16,17]. In some patients, crystals have also been found in the cornea [12,13].…”

“…Most BCD patients notice the first symptoms between the second and fourth decade of life, such as night blindness, decreased central visual acuity, or visual field loss. Progressive visual loss and constriction of the visual fields lead to legal blindness usually in the fifth or sixth decade [9,12,16]. BCD symptoms are similar to those of other retinal degenerative diseases and is frequently misdiagnosed as Retinitis Pigmentosa (RP), choroideremia, Stargardt disease, Late Onset Retinal Degeneration, or other forms of crystalline retinopathies, or can be completely missed [13,15,18,21].…”