Iosifidis C, Liu J, Gale T, Ellingford JM, Campbell C, Ingram S, Chandler K, Parry NRA, Black GC, Sergouniotis PI. Clinical and genetic findings in TRPM1-related congenital stationary night blindness.
Acta Ophthalmol 2022;
100:e1332-e1339. [PMID:
35633130 DOI:
10.1111/aos.15186]
[Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 05/05/2022] [Indexed: 11/27/2022]
Abstract
PURPOSE
Congenital stationary night blindness (CSNB) is a heterogeneous group of Mendelian retinal disorders that present in childhood. Biallelic variants altering the protein-coding region of the TRPM1 gene are one of the commonest causes of CSNB. Here, we report the clinical and genetic findings in 10 unrelated individuals with TRPM1-retinopathy.
METHODS
Study subjects were recruited through a tertiary clinical ophthalmic genetic service at Manchester, UK. All participants underwent visual electrodiagnostic testing and panel-based genetic analysis.
RESULTS
Study subjects had a median age of 8 years (range: 3-20 years). All probands were myopic and had electroretinographic findings in keeping with complete CSNB. Notably, three probands reported no night vision problems. Fourteen different disease-associated TRPM1 variants were detected. One individual was homozygous for the NM_001252024.2 (TRPM1):c.965 + 29G>A variant and a mini-gene assay highlighted that this change results in mis-splicing and premature protein termination. Additionally, two unrelated probands who had CSNB and mild neurodevelopmental abnormalities were found to carry a 15q13.3 microdeletion. This copy number variant encompasses seven genes, including TRPM1, and was encountered in the heterozygous state and in trans with a missense TRPM1 variant in each case.
CONCLUSION
Our findings highlight the importance of comprehensive genomic analysis, beyond the exons and protein-coding regions of genes, for individuals with CSNB. When this characteristic retinal phenotype is accompanied by extraocular findings (including learning and/or behavioural difficulties), a 15q13.3 microdeletion should be suspected. Focused analysis (e.g. microarray testing) is recommended to look for large-scale deletions encompassing TRPM1 in patients with CSNB and neurodevelopmental abnormalities.
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