On this page
Best vitelliform macular dystrophy
BVMD is a genetic disorder leading to progressive central vision impairment. It typically manifests in childhood or adolescence but can vary in severity and age of onset, affecting individuals and families across the UK.
Overview
Best vitelliform macular dystrophy (BVMD) is a type of inherited macular dystrophy, meaning it's a genetic condition that causes damage to the macula. The macula is a small, crucial area in the centre of the retina at the back of the eye, responsible for clear, detailed vision needed for tasks like reading and recognising faces [PMID:33678065]. BVMD is characterised by the accumulation of a yellowish, lipofuscin-like material (resembling an egg yolk) under the macula. This material can disrupt photoreceptor cells and lead to vision problems.
While the condition is present from birth, symptoms often become noticeable in childhood or adolescence. However, the age at which vision changes begin can vary significantly, sometimes not until adulthood [PMID:33678065]. BVMD is estimated to affect approximately 1 in 10,000 people, though the exact prevalence may vary.
Symptoms & clinical features
The primary symptom of BVMD is a gradual decline in central vision. This can manifest as blurred vision, distorted vision (where straight lines appear wavy), or a blind spot in the centre of the visual field. Peripheral vision is typically preserved, meaning individuals can still see things to the sides.
Severity and progression of vision loss can differ greatly between affected individuals, even within the same family [PMID:28755087]. Some people may experience only mild visual disturbances throughout their lives, while others can develop more significant central vision impairment. In the early stages, vision may be near normal, with changes only detectable during an eye examination. As the condition advances, the 'egg-yolk' lesion can evolve, sometimes leading to scarring or abnormal blood vessel growth (choroidal neovascularisation), which can further worsen central vision.
Video: Genetics 101
Affected organs
BVMD primarily affects the macula, which is part of the retina. The retina is a light-sensitive layer at the back of the eye that converts light into electrical signals sent to the brain, allowing us to see. The macula is responsible for high-acuity central vision, necessary for tasks requiring fine detail.
The yellowish material characteristic of BVMD accumulates specifically in the subretinal space, between the retinal pigment epithelium (RPE) - a layer of cells supporting the photoreceptors - and the choroid. This accumulation directly impairs the function of the RPE and the overlying photoreceptor cells in the macula.
Risks & severity
The severity of BVMD can vary widely, even among individuals with the same genetic change. Some people may maintain relatively good vision well into adulthood, while others experience more significant central vision loss earlier in life [PMID:28755087]. The progression of the condition typically involves several stages, starting with a preclinical stage where there are no noticeable symptoms but changes can be seen on examination.
Over time, the characteristic 'vitelliform' lesion may develop, followed by atrophy (thinning) of retinal tissues or, in some cases, the development of abnormal new blood vessels under the retina (choroidal neovascularisation). These complications can lead to more profound and irreversible central vision loss. The lifetime risk of significant central vision impairment varies, but many individuals will experience some degree of visual challenge.
Genetic causes
BVMD is caused by pathogenic variants, also known as mutations, in the *BEST1* gene. This gene provides instructions for making a protein called bestrophin-1. Bestrophin-1 is primarily found in the retinal pigment epithelium (RPE) cells, which are crucial for supporting the light-sensing cells (photoreceptors) in the retina.
The bestrophin-1 protein is thought to be involved in regulating the flow of chloride ions and other substances across the RPE cell membrane [PMID:33678065]. Pathogenic changes in *BEST1* disrupt the normal function of this protein, leading to a build-up of waste products like lipofuscin within the RPE cells. This accumulation results in the characteristic yellowish lesions seen in BVMD and ultimately impairs the function of the macula, leading to vision loss.
- BEST1 bestrophin 1
Inheritance pattern
Best vitelliform macular dystrophy is inherited in an autosomal dominant pattern. This means that a person only needs to inherit one copy of the altered *BEST1* gene from a parent to develop the condition. If a parent has BVMD, there is a 50% chance in each pregnancy that their child will inherit the pathogenic variant and also develop the condition.
This inheritance pattern affects males and females equally. Even if a person inherits the altered gene, the severity of the condition and the age at which symptoms appear can differ, a phenomenon known as variable expressivity. This means that while they will develop the condition, how it affects their vision might be very different from their affected parent or siblings.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosis of BVMD typically begins with a comprehensive eye examination by an ophthalmologist. Specific signs, such as the characteristic 'egg-yolk' lesion in the macula, can be observed. Imaging techniques like optical coherence tomography (OCT) are often used to visualise the retinal layers and detect the subretinal fluid and material accumulation, providing structural detail of the macula's health. Electro-oculography (EOG) is a test that measures the electrical potential across the retinal pigment epithelium and is typically abnormal in people with BVMD, even before vision loss [PMID:28755087].
Confirmation of BVMD is usually achieved through genetic testing, which identifies a pathogenic variant in the *BEST1* gene. In the UK, genetic testing for inherited retinal diseases like BVMD can be accessed through the NHS Genomic Medicine Service (GMS) pathways, often following referral from an ophthalmologist or clinical geneticist. This testing falls under specific R-codes for inherited retinal dystrophies, such as R86 and R87 in England, which help guide diagnostic pathways.
Management & lifestyle
Currently, there is no cure for BVMD, and management focuses on monitoring vision and addressing potential complications. Regular ophthalmological examinations are crucial to track the progression of the condition and detect any changes, such as the development of choroidal neovascularisation (CNV). If CNV occurs, treatments like anti-VEGF injections into the eye may be used to inhibit abnormal blood vessel growth and preserve central vision.
Patients are typically advised to maintain a healthy lifestyle and discuss any concerns about vision changes with their eye care specialist. Low vision aids and rehabilitation services can be beneficial for individuals experiencing significant vision impairment, helping them adapt to daily activities. Support groups and genetic counselling can also provide valuable information and emotional support for affected individuals and their families, offering guidance on the genetic implications and coping strategies.
UK care pathway
In the UK, suspected cases of inherited retinal conditions like BVMD are typically referred to specialist ophthalmology services, often through an NHS consultant. If an inherited cause is suspected, referral to a clinical genetics service or direct access to genetic testing via the NHS Genomic Medicine Service (GMS) laboratory network can be arranged. Genetic testing for inherited retinal dystrophies, including BVMD, is available under specific GMS R-codes. Genetic counsellors play a vital role in explaining the condition, inheritance patterns, and implications for family members, as well as discussing testing options and support services.
Frequently asked questions
Will my vision always get worse if I have BVMD?
The progression of BVMD is highly variable. Some people experience only mild vision changes, while others may have more significant central vision loss. Regular monitoring by an eye specialist helps track changes and manage any complications.
Can children of someone with BVMD inherit the condition?
Yes, BVMD is inherited in an autosomal dominant pattern. If a parent has the condition, each of their children has a 50% chance of inheriting the altered gene and developing BVMD.
Is there a cure for Best vitelliform macular dystrophy?
Currently, there is no cure for BVMD. However, management focuses on regular monitoring, treating complications like choroidal neovascularisation, and using low vision aids to support individuals with vision impairment.
What is the 'egg-yolk' lesion mentioned in BVMD?
The 'egg-yolk' lesion refers to the characteristic yellowish material that accumulates under the macula in BVMD. This material is made up of waste products and can disrupt the normal function of the retina, leading to vision problems.
How is genetic testing for BVMD done in the UK?
Genetic testing for BVMD in the UK is typically initiated by an ophthalmologist or clinical geneticist and performed through the NHS Genomic Medicine Service. It involves a blood test to analyse the *BEST1* gene for pathogenic variants.
References
- Adam MP, Bick S, Mirzaa GM. Bestrophinopathies. 1993. PMID: 20301346
- Tripathy K, Salini B. Best Disease. 2023. PMID: 30725975
- Tsang SH, Sharma T. Best Vitelliform Macular Dystrophy. Advances in experimental medicine and biology. 2018. PMID: 30578489
- Tsang SH, Sharma T. Best Vitelliform Macular Dystrophy. Advances in experimental medicine and biology. 2018. PMID: 30578502
- Altschwager P, Ambrosio L, Swanson EA. Juvenile Macular Degenerations. Seminars in pediatric neurology. 2017. PMID: 28941524
- Jenny LA, Tsang SH, Sharma T. Best Vitelliform Macular Dystrophy. Advances in experimental medicine and biology. 2025. PMID: 40736818
- Xiao Q, Hartzell HC, Yu K. Bestrophins and retinopathies. Pflugers Archiv : European journal of physiology. 2010. PMID: 20349192
- Laich Y, Georgiou M, Fujinami K. Best Vitelliform Macular Dystrophy Natural History Study Report 2: Fundus Autofluorescence and OCT. Ophthalmology. Retina. 2025. PMID: 40086732