Nonsyndromic retinitis pigmentosa is highly prevalent in the Jerusalem region with a high frequency of founder mutations.
OBJECTIVE
Nonsyndromic retinitis pigmentosa (RP) is the most common inherited retinal degeneration, and prevalence of the disease has been reported in populations of American and European origin with a relatively low consanguinity rate. Our aim was to determine the prevalence of nonsyndromic RP in the Jerusalem region, which has a population of about 1 million individuals with a high rate of consanguinity.


METHODS
The patients' clinical data included eye exam findings (visual acuity, anterior segment, and funduscopy) as well as electroretinographic (ERG) testing results under scotopic and photopic conditions. Mutation analysis on a subgroup of patients was performed mainly with candidate gene analysis and homozygosity mapping.


RESULTS
We evaluated the medical records of patients with degenerative retinal diseases residing in the Jerusalem region who were examined over the past 20 years in a large tertiary medical center. A total of 453 individuals affected with nonsyndromic RP were diagnosed at our center, according to funduscopic findings and ERG testing. Based on the estimated population size of 945,000 individuals who reside in the vicinity of Jerusalem, the prevalence of nonsyndromic RP in this region is 1:2,086. The prevalence of RP was higher among Arab Muslims (1:1,798) compared to Jews (1:2,230), mainly due to consanguineous marriages that are more common in the Arab Muslim population. To identify the genetic causes of RP in our cohort, we recruited 383 patients from 183 different families for genetic analysis: 70 with autosomal recessive (AR) inheritance, 15 with autosomal dominant, 86 isolate cases, and 12 with an X-linked inheritance pattern. In 64 (35%) of the families, we identified the genetic cause of the disease, and we revised the inheritance pattern of 20 isolate cases to the AR pattern; 49% of the families in our cohort had AR inheritance. Interestingly, in 42 (66%) of the genetically identified families, the cause of disease was a founder mutation.


CONCLUSIONS
Previous studies showed an approximate prevalence of 1:5,260 on average for nonsyndromic RP in American and European populations. We show that the prevalence in the vicinity of Jerusalem is two-and-a-half times higher due to a high rate of consanguinity and highly prevalent founder mutations within the historically semi-isolated subpopulations we serve.
Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
Dror
D
Sharon
Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
Eyal
E
Banin
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003241:Consanguinity; D005260:Female; D018703:Founder Effect; D005808:Genes, Recessive; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D040582:Inheritance Patterns; D007557:Israel / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D015995:Prevalence; D012174:Retinitis Pigmentosa / Q000453:epidemiology / Q000235:genetics*