Abstract
Purpose :
Retinitis pigmentosa (RP) is a heterogeneous group of progressive inherited retinal disorders (IRD). This retrospective study describe Brazilian patients with RP due to RP1 gene variants (OMIM #180100). RP1 pathogenic variants had been associated with autosomal recessive and dominant RP.
Methods :
We reviewed 529 Brazilian patients with genetic test for IRD. We selected all patients screened with RP1 variants, who underwent a complete ophthalmic examination. Genetic data, medical history and eye exams were collected. The clinical diagnosis was made based on their signs and symptoms, age of onset and fundus features. Databases and web-based programs, including HGMD, OMIM, ExAC, GnomAD, NHLBI EVS, PolyPhen, and SIFT were used to evaluate the RP1 variants.
Results :
Eight unrelated and nonsyndromic RP patients with RP1 variants were selected. Mean age was 31.75±13.9 years, with no gender prevalence. They were all isolated cases. They had classic retinitis pigmentosa with diagnosis at the first decade of life with complains of visual field defect and nictalopia. The visual acuities were severely affected at young age. Some patients had moderate myopia and one had high myopia. The fundus aspects were similar between patients with narrow vessels, pale optic disc and mild osteoclast pigmentation. An atrophic RPE ring was present around the fovea in several cases. All patients had a conclusive molecular diagnosis, with eight different RP1 variants, one of them located in exon 2 and the other seven located in exon 4. This study describes two unpublished mutations - two frameshift duplications (c.1234dupA p.Met412Asnfs*7 and c.1265dupC p.Ala423Cysfs*2) and reinforces other six known mutations – three frameshift deletions (c.469delG p.Val157Trpfs*16; c.3843delT p.Pro1282Leufs*12 and c.4196delG p.Cys1399Leufs*4), two stop gain (c.1186C>T p.Arg396* and c. 1625C>G p.Ser542*) and one missense variant (c.6353G>A p.Ser2118Asn).
Conclusions :
These findings broadened the spectrum of RP1 variants. It highlighted exon 4 as an important part of the gene and the corresponding protein. This study also reviewed the fundus characteristics that clinically could raise the hypothesis of a retinitis pigmentosa due to RP1 gene ahead of genetic test. It is worth to try to identify the disease causing variations since it can provide precise diagnosis, better genetic counselling and new perspectives of treatment.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.