Abstract
Purpose: :
Retinitis pigmentosa (RP) encompasses a group of retinal dystrophies characterized by progressive nyctalopia, peripheral visual field constriction and severe visual loss. The prevalence of RP is 1 in 3500 individuals and is a prototypic example of a genetic heterogeneous disease. Phenotypic differences can be observed within a same RP family suggesting that genetic and/or environmental factors could modify the retinal phenotype. Up to 20% of RP familial cases are autosomal dominant (AD). The most commonly mutated gene in AD RP is rhodopsin (RHO). An atypical form of the disease is sectorial RP, which is associated to RHO mutations. The objective of this study is to describe the clinical and genetic features of a family with sectorial RP due to a missense RHO mutation.
Methods: :
A Mexican family with 3 affected sibs was studied. The Father died at age of 60, while mother died at 80 years old, both without visual impairment. Funduscopy, electroretinogram, and fluorescein retinal angiography were performed. Genetic analysis consisted in PCR amplification and sequencing of the RHO gene in affected subjects.
Results: :
All 3 affected subjects complained from nyctalopia since childhood. Funduscopy revealed sectorial (inferior hemiretina) RP. Diminished visual acuity (20/200, OD, 2/200 OS) with macular involvement was identified in one subject, whereas the remaining 2 had normal macular areas and normal visual capacities. Genetic analysis disclosed a RHO heterozygous c.233A>T transversion, predicting a missense Asn78Ile change in the 3 patients. The mutation was absent in 100 control alleles.
Conclusions: :
A family with sectorial RP due to a RHO mutation is described. Intrafamilial clinical variability was observed in this pedigree. The fact that both parents were visually healthy, suggested an autosomal recessive inheritance. However, this could be explained by sectorial disease not involving macular area in one of them. This case stresses the importance of genotype-phenotype correlation in atypical forms of RP.
Keywords: retinitis • genetics • mutations