Oguchi disease caused by a homozygous novel SAG splicing alteration associated with the multiple evanescent white dot syndrome: A 15-month follow-up

We report a 15-month follow-up case on a Chinese patient with Oguchi disease associated with the multiple evanescent white dot syndrome (MEWDS). The patient’s clinical presentation and follow-up visits were documented via decimal best-corrected visual acuity, fundus photography, fundus autofluorescence (FAF) imaging, near-infrared FAF, spectral domain optical coherence tomography, Humphrey’s visual fields, microperimetry, and multifocal electroretinography. We also performed whole exome sequencing for screening variation in the patient and her relatives. The patient had typical clinical characteristic of Oguchi disease, including night blindness, the Mizuo–Nakamura phenomenon (a golden yellow discoloration of the fundus that disappears in the prolonged dark adaptation [DA]) and typical full-field electroretinogram changes (nearly undetected b-wave in 0.01 and 0.03 ERGs that can partially recover only after prolonged DA). Aside from Oguchi disease, the patient was also diagnosed with the MEWDS based on clinical detections, including suddenly reduced visual acuity, appeared white dots, blurred ellipsoid zone and disrupted interdigitation zone, enlarged blind spot, and reduced macular sensitivity. A series of investigations revealed that along with the 15-month follow-up after onset, the visual acuity enhanced, the numerous white dots disappeared, and the macular structure returned to normal. Moreover, the novel homozygous splicing alteration c.181 + 1G > A was identified in the SAG gene. This work is the first long-term case study of a patient with Oguchi disease associated with the MEWDS. The recovery period of symptoms caused by the MEWDS was much longer than that in typical patients with MEWDS. Molecular genetics demonstrate that this is the first case of Oguchi disease caused by splicing alterations in the SAG gene.