Monozygotic twins with CAPN5 autosomal dominant neovascular inflammatory vitreoretinopathy

Hannah A Rowell,^1,2 Alexander G Bassuk,^3,4 Vinit B Mahajan<sup>1,2

1</sup>Omics Laboratory, ²Department of Ophthalmology and Visual Sciences, ³Department of Pediatrics, ⁴Department of Neurology, University of Iowa, Iowa City, IA, USA

Background: The purpose of this study was to describe the clinical findings in a set of monozygotic twins with autosomal dominant neovascular inflammatory vitreoretinopathy (ADNIV) over a 23-year period.
Methods: A pair of female twins were examined between 26 and 49 years of age. The concordance and discordance of their clinical features were determined. The CAPN5 gene was sequenced using genomic DNA.
Results: Both twins of an affected father demonstrated Stage I ADNIV with mild vitreous cells and a negative b-wave on electroretinography. Genetic analysis confirmed a guanine to thymine nucleotide (c.728G>T, pArg243Leu) mutation in the CAPN5 gene. Over the course of 23 years, each twin progressed to stage III disease, showing posterior uveitis, cystoid macular edema, intraocular fibrosis, early retinal neovascularization, retinal degeneration, and cataract. Disease progression varied moderately between each twin and was asymmetrical between eyes. Twin A had 20/70 and 20/125 in the right and left eye, respectively, and underwent vitrectomy surgery and intravitreal injections with bevacizumab for recurrent cystoid macular edema. Twin B maintained 20/20 and 20/40 in the right and left eye, respectively without intervention.
Conclusion: There was asymmetry between the eyes and some discordance in the rate of disease progression in these monozygotic twins with ADNIV. The overall high disease concordance suggests genetic factors play a major role in clinical manifestations in CAPN5 vitreoretinopathy.

Keywords: autosomal dominant neovascular inflammatory vitreoretinopathy, ADNIV, CAPN5, calpain-5, monozygotic twins