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Ophthalmology – Best’s Vitelliform Macular Dystrophy
Best’s vitelliform macular dystrophy, also known as Best’s disease, is a rare inherited retinal disorder characterized by bilateral involvement of the macula and a distinctive yellow “egg-yolk” lesion. It follows an autosomal dominant inheritance pattern and is caused by mutations in the BEST1 gene on chromosome 11q13, which encodes the bestrophin-1 protein. Although the age of onset is variable, the disease most commonly presents during childhood or adolescence.
The underlying pathophysiology involves dysfunction of bestrophin-1, a calcium-activated chloride channel located in the retinal pigment epithelium (RPE). This dysfunction leads to impaired ion transport and accumulation of lipofuscin between the neurosensory retina and the RPE. Over time, this buildup produces the characteristic vitelliform lesion and contributes to progressive retinal changes.
Patients often present with mild visual symptoms such as blurred vision or metamorphopsia, although some may remain asymptomatic in early stages. A positive family history of retinal dystrophy is an important clue. On examination, the anterior segment is typically normal, while fundus evaluation reveals the classic yellow lesion in the central macula. The disease progresses through several stages, beginning with subtle RPE changes and advancing to the vitelliform “egg-yolk” stage. Later stages may show fragmentation of the lesion (“scrambled egg”), layering of material (pseudohypopyon), and eventual atrophy or scarring. In some cases, complications such as choroidal neovascularization can develop.
Diagnostic testing plays a key role in confirming the diagnosis. A hallmark finding is a normal full-field electroretinogram (ERG) with an abnormal electrooculogram (EOG), reflecting RPE dysfunction. The Arden ratio is typically reduced. Imaging studies such as optical coherence tomography (OCT) demonstrate subretinal deposits and structural changes, while fundus autofluorescence shows increased autofluorescence corresponding to lipofuscin accumulation. Fluorescein angiography may reveal blockage from lesions or leakage if neovascularization is present. Genetic testing can confirm mutations in the BEST1 gene.
There is no specific medical treatment for Best’s disease itself. Management primarily involves observation and regular follow-up with a retina specialist. Patients are monitored for disease progression and complications, particularly choroidal neovascularization. If such complications arise, treatment options include intravitreal anti-vascular endothelial growth factor (anti-VEGF) therapy or photodynamic therapy.
The prognosis is generally favorable, with many patients maintaining visual acuity of 20/40 or better for a significant portion of their lives. However, visual outcomes can vary depending on disease progression and the development of complications. Choroidal neovascularization remains the most important cause of vision loss in affected individuals. Genetic counseling is recommended for patients and their families due to the hereditary nature of the condition.
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