Best Vitelliform Macular Dystrophy (BVMD) is a rare genetic eye disorder that affects the macula, the central part of the retina responsible for sharp central vision. BVMD is also known as Best disease or vitelliform macular dystrophy 2 (VMD2).
The exact cause of BVMD is a mutation in the BEST1 gene, which provides instructions for producing a protein called bestrophin-1. This protein plays a crucial role in the normal functioning of the retinal pigment epithelium (RPE), a layer of cells that supports the photoreceptor cells in the retina.
Genetic Mutation: BVMD is inherited in an autosomal dominant pattern, which means that a person only needs to inherit one copy of the mutated gene from either parent to develop the condition. In some cases, the mutation occurs spontaneously without any family history of the disease. The specific mutation in the BEST1 gene disrupts the normal function of bestrophin-1, leading to the accumulation of lipofuscin deposits in the RPE cells.
Lipofuscin Accumulation: Lipofuscin is a waste material that accumulates naturally in cells as a byproduct of normal cellular metabolism. However, in BVMD, the mutation in the BEST1 gene impairs the ability of RPE cells to process and remove lipofuscin efficiently. As a result, lipofuscin accumulates in the RPE cells, forming characteristic yellowish deposits known as vitelliform lesions.
Progression and Vision Loss: Over time, the vitelliform lesions can progress through different stages, including the formation of a "scrambled egg" appearance and the development of atrophic or fibrotic lesions. As the disease advances, the RPE cells and photoreceptor cells in the macula become progressively damaged, leading to a decline in central vision.
Other Factors: While the primary cause of BVMD is the genetic mutation in the BEST1 gene, other factors may influence the severity and progression of the disease. These factors include age, environmental factors, and additional genetic variations that may modify the disease phenotype.
Conclusion: Best Vitelliform Macular Dystrophy is primarily caused by a mutation in the BEST1 gene, leading to impaired function of bestrophin-1 and subsequent accumulation of lipofuscin in the RPE cells. The disease follows an autosomal dominant inheritance pattern and can progress through various stages, resulting in vision loss over time. While the genetic mutation is the main cause, other factors may contribute to the variability in disease severity among affected individuals.