A large number of gene mutations lead to diseases of the retina. Some such as retinitis pigmentosa are relatively common while others such as the one described here are more rare and limited in distribution. Its name is derived from an area in northern Sweden next to the Bay of Bothnia.
Young children in the first decade of life report difficulty seeing at night (night blindness). Physical examination of the eye may not reveal changes until later but a special test called an electroretinogram documents some damage to the light-responsive cells in the retina. Later in the 2nd and 3rd decades loss of vision becomes pronounced and legal blindness is common among young adults. By then there are obvious pigmentary changes and narrowing of the blood vessels of the retina may be seen. There are no known abnormalities outside of the eye.
This is an autosomal recessive condition requiring that both copies of a specific gene are changed. Parents who carry one copy have normal retinas but each of their children has a 25% chance of developing the condition.
The diagnosis can only be made by an ophthalmologist after an examination of the eye. No treatment is available and many individuals become legally blind before middle age. Tinted lenses though may be helpful.