Best Disease

Updated: Oct 10, 2016
  • Author: Michael Altaweel, MD, FRCSC; Chief Editor: Hampton Roy, Sr, MD  more...
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Overview

Background

Best disease, also termed vitelliform macular dystrophy, is typically an autosomal dominant disorder, which classically presents in childhood with the striking appearance of a yellow or orange yolklike lesion in the macula. Dr Franz Best, a German ophthalmologist, described the first pedigree in 1905. [1]

The lesion evolves through several stages over many years, with increasing potential for adverse visual outcome. A hallmark of the disease is a markedly abnormal electro-oculogram (EOG) in all stages of progression and in phenotypically normal carriers. [2] The adult form varies, as described and shown in the image below.

Adult vitelliform macular dystrophy resembles Best Adult vitelliform macular dystrophy resembles Best disease, but it can be differentiated by its later age of onset, smaller lesion, and normal electro-oculogram testing.
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Pathophysiology

Lesions in Best disease are restricted to the eye. No systemic associations exist. Abnormalities in the eye result from a disorder in the retinal pigment epithelium (RPE). A dysfunction of the protein bestrophin results in abnormal fluid and ion transport by the RPE. [3] Lipofuscin (periodic acid-Schiff [PAS] positive) accumulates within the RPE cells and in the sub-RPE space, particularly in the foveal area. The RPE appears to have degenerative changes in some cases, and secondary loss of photoreceptor cells has been noted. [4] Breakdown of RPE/Bruchs membrane can allow choroidal neovascularization to develop as a late complication.

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Epidemiology

Frequency

United States

Best disease is rare.

International

Best disease is rare.

Mortality/Morbidity

Visual acuity is good in the previtelliform stage. Even with the egg-yolk appearance, visual acuity is maintained in the range of 20/20 to 20/50 (6/6 to 6/15) for many years. The breakup of the vitelliform stage, leading to the scrambled egg stage, may be accompanied by visual acuity deterioration. It is the final stages of geographic RPE atrophy with possible development of choroidal neovascular membrane that is associated with further deterioration in acuity. [5, 6] These changes usually occur in individuals older than 40 years. Various studies have shown that most individuals retain reading and driving vision in at least 1 eye into adulthood (88% have 20/40 or better vision). Only 4% of these individuals develop vision less than 20/200 in the better eye.

Race

Best disease is most common in individuals of European ancestry but can also be found in individuals of African and Hispanic ancestry.

Sex

No known gender predilection exists.

Age

Usual onset of Best disease is from 3-15 years, with an average age of 6 years. The condition often is not detected until much later in the disease because visual acuity may remain good for many years. The atrophic stage usually occurs after age 40 years.

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Prognosis

See Mortality/Morbidity.

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