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Vitelliform Macular Dystrophy: Causes, Treatment & More

Vitelliform macular dystrophy is a rare, inherited eye disorder that can cause progressive loss of central vision and lead to blindness. 

The disorder affects the cells in an area near the center of the retina known as the macula. People with the disease can develop a yellow fatty pigment in the macula that damages the cells and can begin to cause distorted or blurry central vision. This progressively leads to permanent vision loss. 

There are currently no effective treatments for vitelliform macular dystrophy. However, ongoing research and advancements in gene therapy may lead to a treatment in the future.

Vitelliform Macular Dystrophy vs. Macular Degeneration

Both vitelliform macular dystrophy and age-related macular degeneration (AMD) affect the macula of the retina, which can lead to the loss of central vision. The latter develops later in life and may be influenced by genetics, but vitelliform macular dystrophy is undoubtedly inherited. The dissimilarities, however, far outweigh the commonalities between the two disorders.

Key Differences

  • Dystrophy is extremely rare, and degeneration is common, with AMD being one of the leading causes of blindness in adults over 50 years old.
  • People with macular dystrophy get a buildup of a fatty yellow pigment known as lipofuscin in their macula. People with AMD develop yellow deposits known as drusen in their macula or blood vessels leak into the retina.
  • Other than a family history with the disease, there are no known risk factors associated with macular dystrophy, but high blood pressure or high cholesterol, smoking, consumption of saturated fat, and having lighter eye pigment can all contribute to AMD.

Causes of Vitelliform Macular Dystrophy

There are two types of vitelliform macular dystrophy: adult-onset vitelliform macular dystrophy (AVMD) and Best vitelliform dystrophy or Best disease. AVMD develops later in life and Best disease begins in childhood, but both are inherited and involve genetic mutations. 

BEST1 Gene Mutations

Particularly, mutations in the Bestrophin-1, or BEST1, gene cause a variety of degenerative eye disorders, including AVMD and Best disease. 

Patients with a family history of vitelliform macular dystrophy have a chance of developing the disorder themselves. However, there is only a 50% chance that mutations in the BEST1 gene will be passed down, and that doesn’t necessarily mean that the individual will experience symptoms or loss of vision.

Risk Factors

Since vitelliform macular dystrophy is hereditary, there are no risk factors for developing the disorder other than genetics. The only people at risk have a parent who has the mutations in the BEST1 gene. 

If the parent shows no signs of vitelliform macular dystrophy, a person can get their genetic makeup examined through linkage testing.

Symptoms of Vitelliform Macular Dystrophy

Symptoms vary among patients who have vitelliform macular dystrophy depending on the stage of the disorder they are experiencing. 

Mild visual impairment is a symptom during early stages. This includes blurred central vision and not being able to make out certain objects. Patients in later stages experience full loss of central vision. 

Although undetectable by the person with the disease, an ophthalmologist can view legions under the macula of the retina. These yellow fatty pigments get worse and negatively affect central vision as the disease progresses. 

However, peripheral vision remains unchanged during all stages of macular dystrophy since lipofuscin is found exclusively on the center of the eye.

Inheritance 

Vitelliform macular dystrophy is inherited in an autosomal dominant pattern, which means that an affected parent has a 50 percent chance of passing down the altered BEST1 gene to a child. The gene was initially discovered in a case of Best disease, but mutations in the gene are also responsible for AVMD. 

It has been reported that more than 200 mutations of the BEST1 gene generate other similar ocular disorders.

Diagnosis of Vitelliform Macular Dystrophy

Patients who experience symptoms of vitelliform macular dystrophy need to seek medical attention for a proper diagnosis. Genetic examinations and family history are also useful indicators of the presence of AVMD and Best disease.

Testing

There are several different exams an ophthalmologist can perform when testing for vitelliform macular dystrophy, but an electrooculogram (EOG) is typically the most utilized. 

An EOG measures how the retina responds to light. Lower scores on the test can indicate macular dystrophy. 

A funduscopic examination, or fundus exam, also helps properly diagnose the disease by using special lights to view the retina. This helps detect the yellow fatty pigments that are associated with vitelliform macular dystrophy.

Genetics & Family History

An obvious and easy way to indicate if a person has macular dystrophy is if a family member has the disease. A parent carrying the mutated BEST1 gene has a good chance of passing down the ailment, but relatives who have BEST1 mutations can also help identify a family history. This establishes a higher likelihood that a patient will develop vitelliform macular dystrophy. 

Treatment of Vitelliform Macular Dystrophy

There are currently no treatments available for vitelliform macular dystrophy. However, research has been done and is still underway. 

On a genetic level, scientists are currently working to fix BEST1 mutations by replacing broken copies of the gene with non-mutated BEST1 genes. 

Although rare, AVMD and Best disease are still life-altering ailments. With the advancement of genetic research, vitelliform macular dystrophy can hopefully be eradicated altogether in the near future.

References

  1. Adult-Onset Vitelliform Macular Dystrophy Caused by BEST1. (August 2017). Scientific Reports.

  2. Best’s Vitelliform Macular Dystrophy. (October 2008). Medical Journal Armed Forces India.

  3. Best Vitelliform Macular Dystrophy in a Large Brazilian Family. (January 2019). International Journal of Retina and Vitreous.

  4. Electrooculograms for Human–Computer Interaction: A Review. (June 2019). School of Electronic and Biomedical Engineering, Tongmyong University.

  5. Epidemiology of Age-Related Macular Degeneration (AMD): Associations With Cardiovascular Disease Phenotypes and Lipid Factors. (December 2016). Eye and Vision.

  6. The Funduscopic Examination. (1990). Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd edition.

  7. Genetic Testing. (May 2001). National Library of Medicine.

  8. Morphological and Functional Analyses of Adult Onset Vitelliform Macular Dystrophy. (June 2003). British Journal of Ophthalmology.

  9. Sunny Side Up: Vitelliform Dystrophy. (May 2021). Review of Ophthalmology.

  10. UW Researcher Devise Approach to Treat Rare, Incurable Form of Blindness. (2020). School of Medicine and Public Health, University of Wisconsin-Madison.

  11. Case Report on Best Vitelliform Macular Dystrophy: A Cause of Fixation Disparity. (2021). International Journal of Case Reports and Images.

Last Updated November 1, 2022

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