The Classic Vitelliform Macular Dystrophy of Childhood
Best disease (formally, Best vitelliform macular dystrophy) is named for the round, egg-yolk-like deposit that forms beneath the macula in its early stage — 'vitelliform' comes from the Latin for egg-yolk. It usually first shows up on a retinal exam in childhood, sometimes years before a child notices any change in their vision at all, which is part of what makes the condition distinctive: the appearance of the retina and how well a person actually sees do not always move together, especially in the earlier stages.
Best disease moves through a series of recognizable stages as the yellow deposit forms, breaks apart, and eventually resolves. In the earliest 'vitelliform' stage, the lesion is often clearly visible on examination while vision remains normal or only mildly affected. As the deposit enters the 'pseudohypopyon' or 'scrambled-egg' stage, it begins to break apart unevenly, and this is usually when blurred or distorted central vision and difficulty with fine print first become noticeable. In the later atrophic stage, some permanent central vision loss is more established, and a minority of patients develop abnormal blood vessel growth beneath the retina that can cause a further, sometimes sudden, drop in vision.
Best disease is caused by mutations in the BEST1 gene, which produces a protein called bestrophin-1. This protein sits in the retinal pigment epithelium and helps regulate the flow of ions and fluid across that layer. When it malfunctions, fluid and pigment build up abnormally beneath the macula, forming the characteristic vitelliform lesion. Inheritance is autosomal dominant, meaning one mutated copy from either parent is enough to cause the condition — but expressivity varies considerably, so some family members with the identical mutation have a visible lesion with barely any symptoms, while others experience more significant vision change.
The retinal appearance is often distinctive enough that an experienced ophthalmologist can suspect Best disease on examination alone, but confirmation typically involves a few additional tests. Electrooculography (EOG) is particularly useful here, since it shows a characteristically reduced light-rise response even in eyes that still look relatively normal — this can help identify carriers before any visible lesion develops. Optical coherence tomography (OCT) tracks the lesion's stage and any fluid accumulation in detail, and genetic testing for BEST1 confirms the diagnosis and clarifies inheritance for other family members.
There's no treatment that reverses the underlying BEST1 gene defect, so management focuses on monitoring the lesion's stage over time and treating complications as they arise — most notably, abnormal blood vessel growth (choroidal neovascularization), which can sometimes be managed with anti-VEGF injections similar to those used in other retinal conditions. Low-vision aids become more relevant if the lesion progresses to the atrophic stage. Because the disease often has long stable periods, especially in the early vitelliform stage, many people are simply monitored at intervals without active intervention for years at a time.
Best disease has a highly variable course. Many people retain good, functional central vision well into mid-adulthood, particularly if the lesion stays in an earlier stage. Vision loss, when it occurs, tends to happen gradually rather than suddenly — the exception being the minority of cases complicated by abnormal blood vessel growth, which is why periodic monitoring remains valuable even during long quiet stretches.
Not necessarily. Vision and lesion appearance don't always move together in Best disease — a clearly visible lesion can coexist with normal or near-normal vision for years, particularly in the earliest stage.
It's uncommon, but a minority of patients develop abnormal blood vessel growth beneath the retina, which can cause a more sudden drop in central vision. This is one reason for ongoing monitoring even when the disease has been stable.
It's not strictly required for diagnosis in classic cases, but genetic confirmation of the BEST1 mutation is useful for clarifying risk to other family members and for eligibility in any future gene-targeted research.
It's uncommon but reduced-penetrance cases exist, where electrooculography may show the characteristic abnormal signal even without an obvious lesion on examination.