[Genetic causes of hereditary cone and cone-rod dystrophies]

Cone and cone-rod dystrophies belong to the genetically and phenotypically very heterogeneous group of retinal degenerations. This article aims to review the current knowledge of genes and mutations involved in these rare disorders that primarily affect the cone photoreceptor system.

Literature and database search and summary of our own molecular genetic analyses in patients affected by achromatopsia, blue cone monochromatism, and cone and cone-rod dystrophy.

Cone and cone-rod dystrophies can be divided according to the disease course into stationary and progressive disorders or by the genetic mode of inheritance into autosomal-recessive, autosomal-dominant, and X-linked traits. To date, seven genes for autosomal-recessive and nine for autosomal-dominant inherited forms of cone and cone-rod dystrophy, as well as two underlying genes on the X chromosome, have been identified. Linkage analyses imply two additional loci for autosomal-dominant, autosomal-recessive, and X-linked forms of these disorders.

Reliable data on the prevalence and incidence of hereditary cone and cone-rod dystrophies and the underlying genetic defects exist only for distinct clinical and genetic entities. Analysis of the known genes results in identification of the genetic defect and mutation in only a subset of patients.