Purpose: To determine whether the Mizuo-Nakamura phenomenon, which is an important diagnostic sign of Oguchi's disease, also occurs in patients with genetically proven X-linked retinoschisis (XLRS).
Methods: We examined three patients with a clinical and genetic diagnosis of XLRS and one patient who was clinically diagnosed with Oguchi's disease, with an emphasis on the Mizuo-Nakamura phenomenon. We obtained color fundus photographs, especially in the fully dark-adapted state, using the non-mydriatic mode on a digital retinal camera and infrared observation monitor to avoid the bleaching effects caused by the viewing light, which alters the fundus color in a short time.
Results: The Mizuo-Nakamura phenomenon was observed in all patients with molecularly proven XLRS, similar to that in the patient with Oguchi's disease. The sets of photographs were obtained in the light- and dark-adapted states using our newly devised techniques needed to witness the Mizuo-Nakamura phenomenon.
Conclusions and importance: The Mizuo-Nakamura phenomenon was identified in three patients with genetically proven XLRS. To the best of our knowledge, this study provided the first genetic evidence of the Mizuo-Nakamura phenomenon in a patient with molecularly proven XLRS without the causative genetic abnormalities for Oguchi's disease. Our findings suggest that XLRS is responsible for the Mizuo-Nakamura phenomenon and its presence in XLRS is not a rare exception but may be a consistent manifestation of XLRS.
Keywords: G-protein-coupled receptor kinase 1 (RHOK); Mizuo–Nakamura phenomenon; Oguchi's disease; S-antigen visual arrestin (SAG); X-linked retinoschisis; XLRS1.
© 2022 The Authors.