Résumé
Retinitis pigmentosa is a group of inherited disorders of the retina that are characterized by constriction of the visual fields, night blindness, and fundus changes. Polyunsaturated fatty acids especially omega 3 fatty acid docosahexaenoic acid [DHA] is found in high concentration in the rod outer segment membranes of the retina. The aim of the present study is to evaluate the genetic aspects of retinitis pigmentosa among Egyptian patients in relation to fatty acids. Also to evaluate the associated ocular, systemic, and cytogenetic abnormalities aiming to give a proper genetic counseling. We examined 49 patients that attended the Research Institute of Ophthalmology seeking advice in loss of dark adaptation due to retinitis pigmentosa. Patients under study were submitted to full history taking, family pedigree construction, complete clinical and ophthalmic evaluation, cytogenetic studies and biochemical tests to determine plasma level of omega 3 fatty acids, malondialdehyde, and vitamin E. Retinitis pigmnentosa patients were classified into two groups: Primary retinitis pigmentosa group [93.9%], this group included autosomal recessive retinitis pigmentosa [47.8%], autosomal dominant retinitis pigmentosa [13%], X-linked retinitis pigmentosa [8.7%],and sporadic cases [30.5%], and secondary retinitis pigmnentosa group [6.1%], which included 3 male patients with Usher syndrome type I. Our study showed that autosomal recessive variant of retinitis pigmentosa is the most common and severest type in our country with a high rate of consanguinity [91%], so avoid consanguineous marriage may play an important role in preventing this type of retinitis pigmentosa in our society. Cytogenetic analysis for our patients revealed normal chromosomal complement in all patients with different types of retinitis pigmentosa apart from gap in chromosome 6q [chromatic gap] which was reported in 5/20 [25%] of metaphases studied in a male patient presented with autosomal recessive retinitis pigmentosa. Decrease plasma level of vitamin E, and increase plasma level of malondialdehyde was noticed in autosomal dominant and sporadic types of retinitis pigmentosa patients. Consistent decrease in the plasma omega 3 fatty acids especially docosahexaenoic acid [DHA], which was found in most patients with retinitis pigmentosa, may draw the attention upon the use of omega 3 blood level as a laboratory test for relatives of affected patients who are at high risk of having early stages of retinitis pigmentosa. We recommend DHA, and vitamin E supplement for those patients with decrease plasma level of omega 3 fatty acids