What is Bests Disease?
Best's Disease, more commonly referred to as Vitelliform Macular Dystrophy or Best Vitelliform Macular Dystrophy (BVMD), is an inherited eye disorder affecting the macula - the central part of retina responsible for providing sharp and detailed vision. The disorder was named for Friedrich Best from Scotland who first identified it during early 20th century research studies.
Best's disease is typically passed on in an autosomal dominant fashion, meaning an affected individual has a 50% chance of passing the condition onto their children. The cause lies with mutations to the BEST1 gene which plays an essential role in supporting retinal pigment epithelium (RPE), an outer layer of cells located behind photoreceptor cells in the retina.
Best's disease is characterized by yellow deposits called "vitelliform lesions" appearing in the macula, typically of variable size and shape. Over time, this may lead to an overall progressive loss of central vision over time - initially experienced through decreased visual acuity, distortion or difficulty performing tasks that require fine detail or central vision such as reading or recognising faces.
As the disease advances, vitelliform lesions may undergo changes such as thinning, breaking apart, and scar tissue formation, leading to further vision loss as well as other complications like choroidal neovascularization (abnormal blood vessel growth) which may result in leakage of fluid or even bleeding within the macula.
Best's disease typically affects both eyes, although its severity and rate of progression vary depending on an individual. Furthermore, symptoms can begin in childhood or adolescence for some while other may not notice any visual changes until adulthood.
What are the Symptoms of Best’s Disease?
Best's disease (vitelliform macular dystrophy) symptoms vary depending on who's affected and primarily targets the macula - the central part of retina responsible for detailed vision. Here are some symptoms associated with Best's disease:
Blurred or Distorted Central Vision: Best's disease often manifests itself with decreased central vision. This may appear as blurry or hazy vision, difficulty reading small print, difficulty with recognising faces or fine details, difficulty reading small text etc.
Metamorphopsia: Metamorphopsia refers to visual distortion where straight lines may appear wavy or bent, distorting their perception or making objects appear disfigured or misshapen. This symptom may affect object perception as they seem irregularly formed or misshapen.
As Best's disease progresses, a central scotoma - or blind spot - may appear in the central visual field. This means there is loss of vision directly ahead of a person making it more difficult to see objects directly ahead of them.
Vitelliform Lesions: Best's disease is distinguished by yellow or orange-colored deposits known as vitelliform lesions in the macula, typically round or oval in shape and of variable size. They result from lipofuscin buildup within retinal pigment epithelium cells resulting from their accumulation as waste products.
Vision changes: Individuals living with Best's disease may experience fluctuations in their vision. This may involve periods of relatively stable vision followed by sudden shifts or worsening episodes.
Noting the unique progression and severity of Best's disease for every individual can be daunting, however. While some may experience gradual vision decline over time, others may see symptoms rapidly worsen. If you or anyone you know are exhibiting any of the above symptoms it is wise to consult an ophthalmologist or retinal specialist for a thorough eye exam and proper diagnosis.
What are the causes of Best’s Disease?
Best's disease (vitelliform macular dystrophy) is generally caused by mutations to the BEST1 gene. This gene provides instructions for producing bestrophin-1 protein that plays an integral part in maintaining normal functioning of retinal pigment epithelium (RPE), an inner layer that protects photoreceptor cells in the retina.
Best's disease is typically passed down autosomally dominant, meaning a mutation in one copy of the BEST1 gene from either parent is sufficient to trigger symptoms. Rarely, Best's can also be passed on recessively through both copies of its DNA being altered, necessitating two mutations to manifest.
Individuals affected by Best's disease often possess specific mutations of the BEST1 gene that disrupt its normal function and lead to abnormalities within RPE cells and accumulations of lipofuscin waste products inside them, contributing to characteristic macula lesions known as "vitelliform lesions." These lipofuscin deposits contribute to this condition by creating characteristic "vitelliform lesions."
Note that mutations to the BEST1 gene are the primary source of Best's disease; however, their exact mechanisms remain unknown and researchers continue to study this condition in order to gain more insights into its underlying causes and identify possible therapeutic approaches.