Whole exome sequencing detects homozygosity for ABCA4 p.Arg602Trp missense mutation in a pediatric patient with rapidly progressive retinal dystrophy

Maria Carolina Ortube,Stanley F Nelson,Michael B Gorin,Steven Nusinowitz,Ariadna Martinez,Samuel P Strom

doi:10.1186/1471-2350-15-11

Maria Carolina Ortube, Stanley F Nelson + Show 4 more

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https://doi.org/10.1186/1471-2350-15-11

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Abstract

BackgroundA pediatric patient presented with rapidly progressive vision loss, nyctalopia and retinal dystrophy. This is the first report of homozygosity for the p.Arg602Trp mutation in the ABCA4 gene. The child became legally blind within a period of 2 years.Case presentationAn eight year-old Hispanic female presented with bilateral decreased vision following a febrile gastrointestinal illness with nausea and vomiting. Extensive workup involved pediatric infectious disease and rheumatology consultations.Initial visual acuity was 20/60 at distance and 20/30 at near in both eyes. Rapidly progressive vision loss occurred during a 2-year period resulting in visual acuities of 20/200 at distance in both eyes. Fundus exam disclosed attenuated vessels and multiple subretinal blister-like elevations. Optical coherence tomography showed far more lesions than were clinically evident with different levels of elevation. Autofluorescence imagery showed dramatic and widespread geographic areas of atrophy. The deposits that appeared drusen-like on clinical exam were hyperfluorescent, consistent with lipofuscin deposits containing A2e (N-retinylidene-N-retinylethanolamine) indicative of RPE cell dysfunction. Electroretinography was consistent with cone dystrophy, with relative preservation of rod function. Blood analysis and rheumatology evaluation found no evidence of a diffuse post-infectious/inflammatory process. The unique and rapid progression of her subretinal blister-like lesions was documented by fluorescein angiography, optical coherence tomography, autofluorescence imagery, and fundus photography. Family pedigree history disclosed consanguinity, her parents being first cousins. DNA analysis by whole exomic sequencing revealed homozygosity of p.Arg602Trp in the ABCA4 gene.ConclusionThe pediatric patient presented with a striking clinical appearance and dramatic rate of progression that was clinically more characteristic of an infectious or inflammatory process. This case expands the diverse range of phenotypes attributed to ABCA4 mutations and further supports the role of whole exome sequencing as a powerful new tool available to aid clinicians in establishing diagnosis for challenging cases.

Highlights

A pediatric patient presented with rapidly progressive vision loss, nyctalopia and retinal dystrophy
The pediatric patient presented with a striking clinical appearance and dramatic rate of progression that was clinically more characteristic of an infectious or inflammatory process
This case expands the diverse range of phenotypes attributed to ABCA4 mutations and further supports the role of whole exome sequencing as a powerful new tool available to aid clinicians in establishing diagnosis for challenging cases

Summary

Introduction

A pediatric patient presented with rapidly progressive vision loss, nyctalopia and retinal dystrophy. This is the first report of homozygosity for the p.Arg602Trp mutation in the ABCA4 gene. In this report we present a case of early onset and dramatic vision loss progression in a child who underwent multiple ophthalmological and systemic procedures in order to rule out neoplastic, inflammatory or infectious etiologies. After 2 years of ophthalmic follow-up we performed exomic sequencing and identified a likely pathogenic homozygous variant in ABCA4 (p.Arg602Trp) This variant has been reported previously in homozygous form but, except for age of onset, the phenotype associated with this variant is not well described [7,8]

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