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Claudia Yahalom, Adva Kimchi, Michal Macarov, Efrat Shemesh, Ada Rosenmann, Anat Blumenfeld; Albinism in Israel: clinical and genetic characteristics. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1831.
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© ARVO (1962-2015); The Authors (2016-present)
Albinism is a well-known genetic disease causing visual handicap. Our goal is to characterize the prevalence of Albinism, spectrum of visual impairment, clinical findings and causative mutations in a hospital based national referral center for children with low vision in Israel.
Retrospective analysis of patients with clinically confirmed diagnosis of albinism from 1998 to 2017. Phenotypic evaluation included a complete eye examination including visual acuity, nystagmus, transillumination, and degree of foveal development. Genetic analysis included screening of known founder mutations by restriction enzyme digestion or Sanger sequencing, full sequencing of known causative genes by Sanger sequencing, or haplotype analysis. Genetic counseling was given in our center to most families.
We have reviewed the files of 970 albino patients. Genetic diagnosis of albinism was reached in 620 patients. Albino patients were screened for mutations in TYR, P, SLC45A2, GPR143, HPS3 and HPS6 genes, causing OCA1, OCA2, OCA4, OA1, HPS3 and HPS6, respectively. TYR mutations were found in about 67 % of patients, and P mutations were detected in about 28% of patients. While bi-allelic causative mutations were identified in 92.5 % of albinos with TYR mutations, only in 66% of albinos with P mutation both mutations were identified. When only one heterozygous mutation was identified other common genes were ruled out by Sanger sequencing. Visual acuity ranged from 20/32 to 20/630. Among our patients, we found that 24% had a severe reduction in vision (20/200 or worse) and the main mutation causing this severe visual loss was p.G47D in the TYR gene. Genetic counseling offered to patients and families options for prevention of birth of an affected child. Families chose pre-marital testing in 142 cases, pre-natal diagnosis in 95 cases and PGD in 11 cases.
Albinism is a relatively common cause of severe visual impairment and blindness among our population in Israel. TYR and P are the main causative genes among our albino patients. High detection rate was demonstrated for TYR mutations, and this gene is the most common gene linked to severe visual handicap. Genetic counseling and genetic tests can help patients and families to reach a diagnosis and offers the option to decrease the rate of severe visual impairment secondary to albinism in our country.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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