Four Unique Genetic Variants in Three Genes Account for 62.7% of Early-Onset Severe Retinal Dystrophy in Chile: Diagnostic and Therapeutic Consequences.

Leber congenital amaurosis (LCA)/early-onset severe retinal dystrophy (EOSRD) stand as primary causes of incurable childhood blindness. This study investigates the clinical and molecular architecture of syndromic and non-syndromic LCA/EOSRD within a Chilean cohort (67 patients/60 families). Leveraging panel sequencing, 95.5% detection was achieved, revealing 17 genes and 126 variants (32 unique). CRB1, LCA5, and RDH12 dominated (71.9%), with CRB1 being the most prevalent (43.8%). Notably, four unique variants (LCA5 p.Glu415*, CRB1 p.Ser1049Aspfs*40 and p.Cys948Tyr, RDH12 p.Leu99Ile) constituted 62.7% of all disease alleles, indicating their importance for targeted analysis in Chilean patients. This study underscores a high degree of inbreeding in Chilean families affected by pediatric retinal blindness, resulting in a limited mutation repertoire. Furthermore, it complements and reinforces earlier reports, indicating the involvement of ADAM9 and RP1 as uncommon causes of LCA/EOSRD. These data hold significant value for patient and family counseling, pharmaceutical industry endeavors in personalized medicine, and future enrolment in gene therapy-based treatments, particularly with ongoing trials (LCA5) or advancing preclinical developments (CRB1 and RDH12).

Congenital Microcoria: Clinical Features and Molecular Genetics.

Iris integrity is required to regulate both the amount of light reaching the retina and intraocular pressure (IOP), with elevated IOP being a major risk factor for glaucoma. Congenital microcoria (MCOR) is an extremely rare, autosomal dominant disease affecting iris development and hindering both of these functions. It is characterized by absent or underdeveloped dilator muscle fibers and immaturity of the iridocorneal angle-where the aqueous humor is drained-which play a central role in IOP regulation. The dilator muscle anomaly is manifested in pinhole pupils (<2 mm) and thin transilluminable irises, causing both hemeralopia and photoaversion. Axial myopia and juvenile open-angle glaucoma are very frequent (80% and 30% of all cases, respectively). It has been suggested that the immaturity of the chamber angle contributes to glaucoma, and myopia has been ascribed to photoaversion and elevated IOP. Though possible, these mechanisms are insufficient. The disease has been tied to chromosome 13q32.1 structural variations. In addition to compromising iris development, modification of the 13q32.1 architecture could alter signaling pathways for axial ocular length and IOP regulation. Here, we summarize the clinical, histological, and molecular features of this disease, and we discuss the possible etiology of associated anomalies.