Clinical features of a toddler with bilateral bullous retinoschisis with a novel RS1 mutation

PURPOSE: To report the clinical and genetic findings of a male toddler who presented bilateral bullous retinoschisis with a novel RS1 mutation. OBSERVATIONS: This is an observational case report of a patient referred to our hospital with esotropia. A comprehensive ophthalmic examination was performed with the boy (age, 1 year 4 months) under general anesthesia that included fundus examinations, fluorescein angiography (FA), swept-source optical coherence tomography (SS-OCT), and full-field electroretinography (FF-ERG). Genetic analysis of the coding region in the RS1 gene was performed by Sanger sequencing for the patient and mother. There was a family history of X-linked retinoschisis (XLRS). Fundus examinations and FA showed bullous retinoschisis bilaterally in the inferior retina. The SS-OCT images showed two kinds of schisis in the inner nuclear layer (INL) and more proximally. In general, the inner plexiform layer, ganglion cell layer, and retinal nerve fiber layer are in the proximal INL; however, in this case there was hyperreflective tissue with a rough surface instead of normal retinal layers. In addition, in the schisis cavity between the hyperreflective tissue and separated retina, a number of hyperreflective fiber-like strands arose from the hyperreflective tissue and extended to the schisis cavity. During the follow-up period, the bullous retinoschisis collapsed spontaneously in the right eye. FF-ERG showed a reduced b-wave and relatively preserved a-wave in all components. Genetic analysis showed a novel RS1 mutation (c.185_186insT, p.E62DfsX24 in exon 4) in the patient and mother. CONCLUSIONS AND IMPORTANCE: We report the detailed retinal structure in a genetically identified case of bullous retinoschisis. The notable finding was that the cavity of bullous retinoschisis contained a number of fiber-like strands as observed in the cavity of typical retinoschisis.