Simplex Crumbs Homologue 1 Maculopathy Masquerading as Juvenile X-Linked Retinoschisis in Male Patients

We report two unrelated male patients presenting at a young age with decreased vision from a macular dystrophy due to biallelic CRB1 mutations. In addition to a previously-described pathogenic variant, Ile167_Gly169del, two new pathogenic missense variants in CRB1, Thr745Met, and Cys948Tyr are reported here. While CRB1 mutations have been more commonly described in retinitis pigmentosa (RP) and Leber's congenital amaurosis (LCA), we demonstrate that mutations in CRB1 can cause a maculopathy whose initial features can resemble juvenile X-linked retinoschisis (JXLRS). We show that the accompanying macular edema is responsive to carbonic anhydrase inhibitors. With long-term follow-up for each case, we illustrate the natural history of CRB1 maculopathy based on clinical examination and diagnostic imaging.