Genetic counseling in X-linked retinitis pigmentosa

The current status regarding genetic counseling in X-linked retinitis pigmentosa (XLRP) is reviewed. XLRP is the most severe form of retinitis pigmentosa (RP) and leads to blindness in the third or fourth decade of life. The biochemical basis of the disease is not known. Until now genetic counseling in this disease has been dependent on simple Mendelian laws of inheritance and the detection of carriers by clinical and electrodiagnostic means. The limitations with regard to carrier detection are discussed. With the recent advances made in recombinant DNA technology, genetic counseling has come to play an important part in the management of XLRP. The methods of DNA technology and their application to localizing the XLRP gene on the X chromosome are reviewed. The discovery of DNA linkage markers known as restriction fragment length polymorphisms (RFLPs) allow a marker closely linked to a disease gene to be followed through succeeding generations in an affected family. Since linkage studies suggest two XLRP loci, carrier detection and prenatal diagnosis of the disease still remain problematic.