Best disease symptoms usually appear during childhood or early adolescence, but some people may only start experiencing problems later in life. The severity of symptoms can also vary between individuals.
Best disease causes a progressive loss of central vision and a reduction in visual sharpness (visual acuity), which leads to challenges with reading, watching TV, driving, and seeing the screen of a phone or computer. There may also be difficulties in recognising colour, and straight-shaped objects like lamp posts can sometimes appear to be curvy. Some people experience photophobia, an extreme sensitivity to light.
Visual acuity tends to deteriorate gradually but without ever reaching the point of complete sight loss. Despite progressive central visual loss, Best disease does not typically affect the outer parts of the retina, so affected individuals tend to retain reasonable peripheral vision that enables navigation.
Best disease is caused by mutations in the BEST1 gene. The gene carries information for the production of the protein bestrophin-1, which can be found in the retinal pigment epithelium (RPE), a layer of cells that supports the light-sensing photoreceptors in the retina. Best disease belongs to a group of conditions called bestrophinopathies.
Best disease is usually inherited in an autosomal dominant pattern, but recessive inheritance is also possible, depending on the exact nature of the genetic fault in the BEST1 gene. A genetic test can confirm the inheritance pattern.
As with other macular dystrophies, vitamin A supplementation should be avoided by those living with Best disease.