ABSTRACT
For many years, ophthalmologists were well aware of the fact that in some cases, retinitis pigmentosa is associated with extraocular abnormalities. Well-known examples were the polydactyly and other abnormalities of what is now called Bardet-Biedl syndrome or the hearing impairment of Usher syndrome. Mutational analysis will detect that some syndromic retinitis pigmentosa (RP) entities and isolated RP are all caused by mutations of the same genes. These will usually be mutation-specific, meaning that the same gene with a different disease-bearing mutation will cause isolated RP, while another mutation will cause a disease included in syndromic RP. In other entities, the disease results from a specific, distinct gene.
