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Maria Isabel Lopez Molina, Blanco-Kelly Fiona, Martinez Garcia Monica, Ayuso Carmen, Corton Marta, Trujillo-Tiebas Maria Jose; Albinism in Spain: Current genetic picture. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6580.
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© ARVO (1962-2015); The Authors (2016-present)
Classically albinism was understood as hypopigmentation but nowadays visual impairment (decreased visual acuity, foveal hypoplasia, altered stereoscopic vision and iris transillumination) defines the condition, together or not with hypopigmentation of skin, hair and/or eyes. Albinism is a group of rare inherited disorders genetically and phenotypically heterogeneous. Non-syndromic albinism, the most common form worldwide, can be classified as ocular albinism (OA) with X-linked inheritance (GPR143 gene) and oculocutaneous albinism (OCA) with autosomic recessive inheritance pattern (TYR, OCA2, TYRP, SLC45A2, SLC24A5 and C10orf11 genes). TYR and OCA2 are the most frequent mutated genes in albino Caucasian population. In this work, we have performed a transversal study of our Spanish cohort of albino patients genetically characterized.
A total of 55 patients with clinical suspicion of albinism were recruited and studied at the Genetics department of IIS-FJD, including 31 OCA and 24 OAs patients. Genetic analyses were performed by Sanger sequencing for mutational screening of TYR, OCA2 and GPR143 genes, and also by MLPA assays (MRC-Holland® P325-A1 and P054 kits) for deletions/duplications of OCA2, TYR and GPR143 genes.
Twenty-one (68%) OCA patients presented point mutations and/or deletions, 18/21 (86%) in TYR and 3/21 in OCA2. In 44% (8/18) of the TYR-mutated patients and in 66% (2/3) of the OCA2-mutated patients, only one mutated allele was identified. The most frequent mutations in TYR gene were p.Arg217Trp and p.Gly47Asp, accounting for 18% and 15% of the detected mutated alleles, respectively.Nearly 40% of patients with a clinical diagnosis of OA were genetically characterized, four carrying an hemizygous mutation in the GPR143 gene and five patients with mutations in OCA-associated genes (4 TYR and 1 OCA2).
Up to date, 50% of the albino patients of our cohort have been genetically characterized, being TYR the most prevalent mutated gene. A considerable percentage of these patients lacks the identification of the second mutation, fortunately new coming technologies will allow us to complete the genetic diagnosis. Study of OCA genes (mainly TYR and OCA2) is recommended in OA patients with negative result for GPR143, as mild phenotypes can be misdiagnosed as OA.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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