Overview
Bietti crystalline dystrophy is an autosomal recessive chorioretinal dystrophy caused by mutations in CYP4V2, encoding a cytochrome P450 enzyme involved in fatty acid metabolism. It is characterized by glistening crystalline deposits in the cornea and retina, progressive atrophy of the RPE and choroid, and night blindness progressing to severe visual impairment. The condition is more prevalent in East Asian populations.
Genetics
Caused exclusively by CYP4V2 mutations. Over 50 mutations identified; c.802-8_810del17insGC is the most common in East Asian patients. Inheritance is autosomal recessive.
| Gene | Locus | Inheritance | Notes |
|---|---|---|---|
| CYP4V2 | 4q35.2 | AR | Cytochrome P450 family 4 subfamily V member 2; sole known cause |
Clinical Presentation
Early
- Night blindness
- Crystalline deposits visible on fundus exam
- Reduced peripheral vision
Progressive
- Chorioretinal atrophy
- Reduced visual acuity
- Photophobia in some patients
Advanced
- Severe visual field loss
- Legal blindness (typically 4th–6th decade)
- Corneal crystals (limbal area)
Diagnosis
- Fundus: Glistening crystalline deposits + chorioretinal atrophy
- Slit-lamp: Corneal crystals at limbus (not all patients)
- ERG: Reduced rod and cone responses
- OCT: Outer retinal atrophy, crystal hyperreflectivity
- Genetic testing: CYP4V2 sequencing
Current Research & Treatment
No approved treatments exist. CYP4V2 gene therapy is in active clinical development; a Phase 1/2 trial (NCT03912727) showed safety and preliminary efficacy. This is one of the most advanced gene therapy programs for a rare chorioretinal dystrophy.
Active Clinical Trials
The following active clinical trials are investigating treatments for Bietti Crystalline Dystrophy. Trial status and enrollment may change; always verify directly on ClinicalTrials.gov.