Introduction
Bietti's crystalline dystrophy is an AR condition affecting the CYP4V2 gene, which is a cytochrome responsible for fatty acid metabolism and is apart of the large CYP450 family.
- The inability to metabolise fatty acids leads to the buildup of crystalline lipid deposits
- These deposits can be found on both the cornea and retina
- It has an onset around the 2nd or 3rd decade
- Accompanied by nyctalopia, VF constriction
Dead Giveaways
By far the biggest giveaway is the retinal examination
Fundus Examination
So shiny!! This is associated RPE and choriocapillaris atrophy.
FAF:
FAF reveals the areas of chorioretinal atrophy, usually surrounded by a region of relative hyper-AF
Crystalline aspects still visible. Areas of chorioretinal atrophy also evident in hypo-AF
diagnostic features
Less conclusive features of BCD includes the cornea and OCT, featuring qualities found in other diseases, such as corneal dystrophies, and chorioretinal atrophy.
Cornea:
Corneal crystals can appear in the periphery near the limbus, but is not the primary feature
OCT:
The OCT highlights the chorioretinal atrophy, as well as the loss of the EZ
The EZ layer is disrupted, and the RPE-Bruch's complex is almost fully attenuated. The choriocapillaris is also very difficult to make out. The white arrows indicate location of the crystalline deposits in the outer retinal