Novel biallelic TRPM1 variants in an elderly patient with complete congenital stationary night blindness
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CLINICAL CASE REPORT
Novel biallelic TRPM1 variants in an elderly patient with complete congenital stationary night blindness Takaaki Hayashi
. Kei Mizobuchi
. Shinsuke Kikuchi . Tadashi Nakano
Received: 13 July 2020 / Accepted: 1 October 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Background Little is known about whether patients with complete congenital stationary night blindness (CSNB) maintain visual function throughout their lifetime. The purpose of this report was to describe clinical and genetic features of an elderly female patient with complete CSNB that we followed for 5 years. Methods Molecular genetic analysis using wholeexome sequencing (WES) was performed to detect disease-causing variants. We performed a comprehensive ophthalmic examination including full-field electroretinography (ERG). Results In the patient, WES identified two novel variants (c.1034delT; p.Phe345SerfsTer16 and c.1880T[A; p.Met627Lys) in the TRPM1 gene. Her unaffected daughter has one of the variants. The patient reported that her visual acuity has remained unchanged since elementary school. At the age of
T. Hayashi (&) K. Mizobuchi S. Kikuchi T. Nakano Department of Ophthalmology, The Jikei University School of Medicine, Tokyo 105-8461, Japan e-mail: [email protected] T. Hayashi Department of Ophthalmology, Katsushika Medical Center, The Jikei University School of Medicine, 6-41-2 Aoto, Katsushika-ku, Tokyo 125-8506, Japan S. Kikuchi Kikuchi Eye Clinic, Tokyo 192-0904, Japan
68 years old, fundus and fundus autofluorescence imaging showed no remarkable findings except for mild myopic changes. Goldmann perimetry showed preserved visual fields with all V-4e, I-4e, I-3e and I-2e isopters. Optical coherence tomography demonstrated preserved retinal thickness and lamination. Rod ERG showed no response; bright-flash ERG showed an electronegative configuration with minimally reduced a-waves, and cone and 30-Hz flicker ERG showed minimally reduced responses. Overall, the ERG findings of ON bipolar pathway dysfunction were consistent with complete CSNB. Conclusions This is the oldest reported patient with complete CSNB and biallelic TRPM1 variants. Our ophthalmic findings suggest that some patients with TRPM1-related CSNB may exhibit preserved retinal function later in life. Keywords Autosomal recessive inheritance TRPM1 gene Retina Congenital stationary night blindness Full-field electroretinography
Introduction In 1952, Schubert and Bornschein [1] reported a form of congenital stationary night blindness (CSNB), a non-progressive retinal disorder, in which the scotopic electroretinographic a-wave was preserved but the
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b-wave was severely reduced, resulting in an electronegative waveform. In 1986, the CSNB form was divided into two types, complete and incomplete CSNB, based on the absence or presence of b-wave responses in rod electroretinography (ERG), respectively [2]. Patients with complete CSNB present with night bli
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