In silico prediction tools and protein structural modelling were used to evaluate the pathogenicity and functional impact of the GNAT1 p.Gln200Arg variant respectively.<h4>Results</h4>Our proband, a 21-year-old transgender male, and his 62-year-old mother had a lifelong history of nyctalopia and visual acuity of 6/6 OU. The gene discussed is GNAT1; the disease is night blindness.