Best disease, also known as Vitelliform Macular Dystrophy type 2 (VMD2), is a heritable disorder occurring primarily in European Caucasians characterized by the presence of a vitelliform macular lesion leading to the classic egg-yolk appearance in genetically predisposed individuals
- Autosomal dominant inheritance
- Only disease with a relatively normal ERG with abnormal EOG results
Bestrophinopathies:
Spectrum of ophthalmic disorders caused by pathogenic variants in BEST1, are typically characterized by retinal degeneration.
- Best vitelliform macular dystrophy (BVMD) (AD)
- Adult-onset vitelliform macular dystrophy (AVMD) (AD)
- Autosomal dominant vitreoretinochoroidopathy (ADVIRC) (AD)
- Autosomal recessive bestrophinopathy (ARB) (AR)
Clinical features
Individuals with Best disease generally show a gradual loss of visual acuity starting in their teenage years, although the frequency with which an affected individual may show symptoms and the severity of those symptoms are highly variable.
Complication:
- Secondary choroidal neovascularization (CNV) (severe complication)
Fundus examination:
Characteristic presentation is by bilateral fundus changes of egg-yolk appearance (as in a fried egg with sunny side up) at the macula in both eyes.
- Stage 1 (previtelliform stage): Normal macula or subtle RPE pigment changes, EOG is abnormal and visual acuity (VA) is 20/20.
- Stage 2 (vitelliform stage): Well-circumscribed, 0.5-5 mm round, elevated, yellow or orange lesion bearing an egg-yolk appearance; usually centered on the fovea; may be multifocal; rest of the fundus has a normal appearance. VA is 20/20 to 20/50.
- Stage 3 (pseudohypopyon stage): Yellow material breaks through the RPE which accumulate in the subretinal space in a cyst with a fluid level. The yellow material shifts with extended changes in position (60-90 min). This stage most often is found in the teenage years, but it has been described in individuals aged 8-38 years. VA is 20/20 to 20/50.
- Stage 4 (vitelloruptive stage): Scrambled egg appearance due to break up of the uniform vitelliform lesion. Pigment clumping and early atrophic changes may be noted. Visual acuity may deteriorate moderately. VA is 20/20 to 20/100.
- Stage 5 (atrophic stage): Disappearance of the yellow material over time and an area of RPE atrophy remains. This appearance is difficult to distinguish from other causes of macular degeneration. Visual acuity can deteriorate more markedly at this stage. VA may reduce to less than 20/200.
- Stage 6 (CNVM/cicatricial stage): Occurs after the atrophic stage, where choroidal neovascularisation may develop and leading to a whitish subretinal fibrous scar.
Optical coherence tomography (OCT):
- Vitelliform materials below photoreceptor layer as a dome-shaped, hyperreflective and homogenous lesion
Management
Best vitelliform macular dystrophy without choroidal neovascular membrane (CNVM)
Needs no treatment
- Regular follow up (vital for early detection of complications, especially CNVM)
BVMD with choroidal neovascular membrane (CNVM):
- Anti-VEGF agents:
- Bevacizumab
- Ranibizumab
- Aflibercept
- Laser and photodynamic therapy