Genotype–phenotype correlations in Bothnia dystrophy caused byRLBP1gene sequence variations

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Abstract

Purpose:

To evaluate phenotypes caused by differentRLBP1mutations in autosomal recessive retinitis pigmentosa of Bothnia type.

Methods:

Compound heterozygotes for mutations in theRLBP1gene [c.677T>A]+[c.700C>T] (p.M226K+p.R234W),n= 10, aged 7–84 years, and homozygotes c.677T>A (p.M226K),n= 2, aged 63 and 73 years, were studied using visual acuity (VA), low-contrast VA, visual fields (VFs) and optical coherence tomography (OCT). Retrospective VA and VFs, standardized dark adaptation and full-field electroretinograms (ERGs) were analysed and prolonged dark adaptometry and ERG (at 24 hr) were performed.

Results:

Progressive decline of VA and VF areas was age-dependent. Retinal degenerative maculopathy, peripheral degenerative changes and retinitis punctata albescens (RPA) were present. Early retinal thinning in the central foveal, foveal (ϕ 1 mm), and inner ring (ϕ 3 mm) in the macular region, with homogenous, high-reflectance RPA changes, was visualized in and adjacent to the retinal pigment epithelium/choriocapillaris using OCT. Reduced dark adaptation and affected ERGs were present in all ages. Prolonged dark adaptation and ERG (at 24 hr), an increase in final threshold, and ERG rod and mixed rod/cone responses were found.

Conclusions:

The twoRLBP1genotypes presented a phenotypical and electrophysiological expression of progressive retinal disease similar to that previously described in homozygotes for the c.700C>T (p.R234W)RLBP1mutation. The uniform phenotypical expression ofRLBP1mutations is relevant information for the disease and of importance in planning future treatment strategies.

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