Symptoms
Symptoms vary widely depending on the stage of the disease. Some individuals may have no symptoms initially. Common symptoms include:
Blurred or distorted central vision
Difficulty reading
Difficulty recognizing faces
Reduced color vision
A yellow or orange round lesion (the "egg yolk") in the macula, visible during an eye exam.
Metamorphopsia (straight lines appear wavy)
Causes
Best disease is caused by mutations in the BEST1 gene, which provides instructions for making a protein called bestrophin-1. Bestrophin-1 is a chloride channel protein found in the retinal pigment epithelium (RPE), a layer of cells beneath the photoreceptors in the retina. Mutations in *BEST1* disrupt the function of this protein, leading to the accumulation of lipofuscin under the macula. It is typically inherited in an autosomal dominant pattern, meaning that only one copy of the mutated gene is sufficient to cause the disease. However, spontaneous mutations can also occur.
Medicine Used
There is currently no cure for Best disease, and no specific medication can directly reverse the underlying genetic defect or remove the lipofuscin accumulation. Treatment focuses on managing symptoms and preventing complications:
Low vision aids: Magnifiers, special lighting, and other adaptive devices can help individuals maximize their remaining vision.
Anti-VEGF injections: In some cases, choroidal neovascularization (CNV) can develop, where new blood vessels grow under the retina. Anti-VEGF injections (e.g., bevacizumab, ranibizumab, aflibercept) can help to reduce the growth of these vessels and prevent further vision loss.
Photodynamic therapy (PDT): If CNV is present, PDT may also be considered.
Is Communicable
No, Best disease is not communicable. It is a genetic disease caused by mutations in the BEST1 gene and is not contagious.
Precautions
Since Best disease is a genetic condition, there are no specific precautions to prevent its development in an individual who has inherited the gene mutation. However, the following measures are important:
Regular eye exams: Early detection and monitoring of the disease progression are crucial.
Genetic counseling: Individuals with a family history of Best disease may consider genetic counseling to understand the risk of inheriting or passing on the condition.
Protecting vision: Avoiding smoking and maintaining a healthy lifestyle may help to support overall eye health.
How long does an outbreak last?
Best disease is not an "outbreak" type of illness. It is a chronic, progressive condition that can last a lifetime. The progression of symptoms and vision loss varies significantly among individuals.
How is it diagnosed?
Diagnosis of Best disease typically involves a comprehensive eye exam, including:
Visual acuity testing: To measure sharpness of vision.
Fundoscopy: To examine the retina and macula for characteristic signs of Best disease (e.g., the "egg yolk" lesion).
Optical coherence tomography (OCT): To obtain detailed images of the retinal layers and assess the extent of lipofuscin accumulation.
Electrooculogram (EOG): A test that measures the electrical activity of the eye and is typically abnormal in Best disease.
Fluorescein angiography (FA): To evaluate for the presence of choroidal neovascularization (CNV).
Genetic testing: To confirm the diagnosis by identifying mutations in the BEST1 gene.
Timeline of Symptoms
The timeline of symptoms in Best disease is variable, but generally follows these stages:
Previtelliform stage: The retina may appear normal, with no symptoms or subtle changes detectable on examination.
Vitelliform stage (Egg-Yolk stage): A yellowish, round lesion resembling an egg yolk develops in the macula. Vision may be relatively normal at this stage, or there may be mild blurring or distortion. Typically appears in childhood/adolescence.
Pseudohypopyon stage: The "egg yolk" lesion may partially resolve, with a layering effect resembling a hypopyon (a collection of pus in the anterior chamber of the eye).
Vitelliruptive stage (Scrambled-Egg stage): The lesion breaks apart and appears more irregular. Vision may worsen.
Atrophic stage: The lipofuscin material disperses, leaving an atrophic scar in the macula. Vision loss can become more significant.
Complications: CNV can develop at any stage, leading to rapid vision loss.
Important Considerations
Genetic counseling and testing: Crucial for families with a history of Best disease.
Regular monitoring: Lifelong monitoring by an ophthalmologist is necessary to track disease progression and manage complications.
Impact on daily life: Vision loss can affect activities such as reading, driving, and recognizing faces. Low vision aids and support services can help individuals adapt.
Variability: The severity and progression of Best disease can vary significantly among individuals, even within the same family.
Research: Ongoing research is focused on understanding the underlying mechanisms of Best disease and developing new treatments.