Welcome to bestdisease.net. The purpose of this website is to share my story of living with Best disease and to hopefully explain to you what this disease is and what it does to those who have it. I will also attempt to stay abreast of any research that may be beneficial to this incurable disease and post links to articles and journals that will help you stay up-to-date on the progress.

What is Best Disease?

Best disease is also called Best vitelliform macular dystrophy. It is an eye disease that is slowly progressive and usually starts becoming an issue when someone is a child or young adult. It is characterized by a loss of central vision. The severity of vision loss is quite variable. Usually Best disease affects both eyes, but occasionally it can be unilateral. Additional lesions outside the macula of non-foveal lesions have been found in some cases. Doctors classify Best disease into mutliple stages. (See Table 2 in this link) Microscopy shows that Best disease patients have an accumulation of lipofuscin granules in the retinal pigment epithelial of the macula and other parts of the retina.

There are several tests that are used to identify Best disease. The first is the electro-oculogram (EOG) which measures the resting potential of the retina. Resting potential is the cell membrane potential that would be present if there were no action potentials or other changes to the membrane potential. Usually this is a negative number in normal eye. For patients with Best disease the EOG is usually abnormal with a reduced light peak/dark trough ratio. The light peak/dark trough ratio does not appear to relate to the severity of the disease. Another test for Best disease is the electroretinogram (ERG). The ERG measures electrical responses of the rods and cones in the retina as well as ganglion cells. In patients with Best disease this test is usually normal. Slight reduction in wave amplitudes may be seen. A third test for Best disease is optical coherence tomography (OCT). This test is used to create a cross section view of the retina. OCT findings change depending on the stage of the disease.

Genetic testing is available to test for the abnormal Best disease gene. Best disease is inherited in an autosomal dominant pattern. This means that if a parent has Best disease then each of their children has a50% chance of inheriting the abnormal gene. VMD2 is the gene that has been associated with Best disease. The normal bestrophin gene has 585 amino acids. The abnormal genes produced in Best disease are typically missense or truncated. Genetic testing does not always give absolute answers. It is possible to test negative for the gene mutation and still have Best disease. As well, the genetic test may miss large mutations in the gene and not recognize the condition as Best disease. One study notes that detection rates for gene mutations is much higher for those individuals with a family history of Best disease. This means that the sequence analysis pick up around 96% of affected people with a family history of Best disease, but only 50-70% of people with no family history. Penetrance of the abnormal gene appears to be essentially complete, with rare exception.