32.1 Features

Autosomal dominant (AD) cases have early age of onset and diagnosis occurs in early childhood to teenage years. In a minority of patients, a choroidal neovascular membrane (CNVM) can form in the setting of surrounding atrophy. Vision may also decline due to fibrosis or geographic atrophy. Autosomal recessive (AR) cases have vision loss in the first or second decades of life and worse vision than those with AD form of disease. Genetic testing for Best disease reveals a mutation in the BEST1 gene encoding the bestrophin protein that is located in the basolateral membrane of the retinal pigment epithelium (RPE). Over 100 mutations in the BEST1 gene have been reported.

32.1.1 Common Symptoms

It may be asymptomatic with normal vision in the early stages. Other symptoms include reduction in central visual acuity and/or metamorphopsia.

32.1.2 Exam Findings

Best disease can progress at variable rates not corresponding to the classical staging of the disease. It can also present as a multifocal process, especially in the recessive form, with several vitelliform lesions in the retina.

Autosomal Dominant Best Disease

Traditionally described with a progressive staging system. However, many patients may remain in the same stage that they were in at the time of diagnosis.

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  Stage 1: posterior pole will look normal on fundus examination and vision is normal.

  
  
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  Stage 2: some RPE window and granularity defects may be seen with or without a yellow foveal dot.

  
  
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  Stage 3: a yellow, well-circumscribed, homogeneous, “yolk-like” appearing (vitelliform) macular lesion is present (▶ Fig. 32.1). Vision may be slightly reduced.

  
  
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  Stage 4: characterized by a layering of the vitelliform lesion due to fluid resorption, resulting in a pseudohypopyon appearance as the material moves inferiorly (▶ Fig. 32.2).

  
  
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  Stage 5: the vitelliruptive stage. The lesion will “scramble” and vision can significantly decrease.

  
  
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  Stage 6: characterized by RPE atrophy.

  
  
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  Stage 7: the cicatricial stage. Choroidal neovascularization (CNV) may be present, which often is bilateral and symmetric (▶ Fig. 32.3).

  
  
  
  

  

  
  

  Fig. 32.1 Fundus photograph demonstrating the classic “yolk-like” round vitelliform lesion in the macula.

  
  
  
  

  

  
  

  Fig. 32.2 Layering of the vitelliform lesion from fluid resorption resulting in a pseudohypopyon appearance.

  
  
  
  

  

  
  

  Fig. 32.3 Advanced Best disease with subretinal fibrosis in the center of the macula.

Autosomal Recessive Best Disease

This form often presents with hyperopia. Cystoid macular edema or extensive subretinal fluid are present, sometimes encompassing most of the macula. Single or multiple vitelliform lesions may be visible with flecks inside and outside the macula (▶ Fig. 32.4). Subretinal fibrosis is more common than in the AD form. CNVMs may also occur. Genetic testing reveals mutations in both BEST1 alleles, with patients being most commonly compound heterozygotes.

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