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E Wolf, P Bernstein; Discordant Retinitis Pigmentosa in Monozygotic Twins . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3951.
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Purpose:The authors characterize the clinical and laboratory findings of a woman with severe progressive simplex retinitis pigmentosa (RP) and her unaffected monozygotic twin. Methods:The diagnosis of simplex RP was established in one of two proven monozygotic twins (by RFLP testing) and ruled out in her sister using pedigree review, serial clinical exams, Goldman visual fields, electroretinography, and fluorescein angiography. Cytogenetic analysis, screening for rhodopsin mutations, and screening for anti-retinal antibodies was performed. Results:Monozygotic twins were followed clinically over a 6 year period. Family pedigree review revealed no relevant ocular disease history. The affected twin developed severe bilateral progressive RP with cystoid macular edema, while her sister remained unaffected, with normal electroretinography and visual fields. No known chromosomal abnormalities or rhodopsin mutations were found in either twin. Both twins tested positive for known anti-retinal antibodies (anti-enolase/carbonic anhydrase/recoverin). The incidence of simplex RP in monozygotic twins is estimated to be 1 per 2.9 million population, or 9 per 1000 monozygotic twin pairs. Conclusion:This is the first reported case of discordant RP in monozygotic twins. Thus, simplex RP may result from postconception environmental factors or mutational mechanisms, clinically mimicking inherited RP. Surprisingly, both twins were found to have anti-retinal antibodies, particularly anti-enolase antibody, which has been previously associated with simplex RP. Thus, anti-retinal antibodies may not be pathogenic, nor a reliable marker for RP.
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