Clin zyxwvutsrqponm Genet 1993: 44: 232-235 Prinfed m Denmark zyxwvutsrqponm , All rights reserved Copyright zyxw 0 Munksgaard 1993 zyx CLINICAL GENETICS ISSN 0009-9163 Retinitis pigmentosa in Southern Africa Greenberg J, Bartmann L, Ramesar R, Beighton P. Retinitis pigmentosa in Southern Africa. Clin Genet 1993: zyxwvutsr 44: 232-235. zyxwvut 0 Munksgaard, 1993 Retinitis pigmentosa (RP) is a heterogeneous group of inherited retinal disorders which are a common cause of genetic blindness. The relative frequencies of the different forms of RP in South Africa, zyxwvu as determined from the register at the DNA banking centre for RP at the Department of Human Genetics, University of Cape Town, are presented and discussed. Of the 125 families analysed, 29 (23%) showed autosomal dominant, 33 (27%) autosomal recessive and 3 (3%) X-linked inheritance. In 10 families the pedigree data were insufficient to allow accurate genetic subtyping and a further 50 patients were sporadic without a family history of RP or other syndromic features which would allow categorization. Retinitis pigmentosa (RP) is a heterogeneous group of inherited degenerative retinal disorders which classically present with constricted visual fields and night blindness; fundoscopy reveals ab- normal accumulation of pigmentation in the retina. The age of onset of symptoms, rate and pro- gression correlate, to some extent, with the mode of inheritance. Affected individuals have abnormal electroretinograms (ERGS) in the early stages and significant visual handicap is usually present by middle age. The condition may be transmitted as an auto- soma1 dominant (AD), an autosomal recessive (AR) or an X-linked (XL) trait; RP may also occur sporadically and it may be a component of a num- ber of genetic syndromes. Molecular studies of each genetic type of RP have revealed that there is both allelic and nonallelic heterogeneity, al- though the phenotypic and pathological changes in all three genetic forms are essentially identical. The relative frequencies of the different genetic forms of RP vary in different populations through- out the world. Published studies comparing the proportions of the different genetic types of RP in various parts of the world are presented in Table 1. South African families with RP have been docu- mented in our department during the past 21 years. We have analysed our data, calculated the pro- J. Greenberg, 1. Bartmann, R. Rarnesar and P. Belghton MRC Research Unit for Medical Genetics, Department of Human Genetics, University of Cape Town, Medical School, Observatory 7925, South Africa Key words: genetic forms - retinitis pigmentosa - syndromic RP Dr. Jacquie Greenberg, Department of Human Genetics, University of Cape Town Medical School, Observatory 7925, Republic of South Af rim Received 26 January, revised version received 3 May, accepted for publication 25 May 1993 portions of the different types of RP according to the mode of inheritance and compared them with previous reports from various parts of the world. Our findings are presented and discussed in this paper. Patlents and methods RP patients and families referred to our depart- ment since 1972 have been documented and their records have been maintained. Based on this ma- terial and following a nation-wide survey, Oswald et al. (1985) published an overview of RP in South Africa (SA). Although the reported figures were recognised as being incomplete, the relative fre- quencies of the various types of R P that were found at that time provided a perspective of RP in this country. A DNA Banking Centre was established in the molecular laboratory of the Department of Human Genetics, University of Cape Town (UCT) with support from the RP Foundation of SA. In collab- oration with the Department of National Health and Population Development, genetic nursing sis- ters throughout the country conduct home visits in order to obtain blood specimens and collect pedigree data. As part of the protocol, arrange- ments are made for RP family members to have diagnostic evaluation at the Department of Oph- z 232