Congenital microcoria (MCOR) is a rare inherited ocular disorder. Here, we describe a novel nonsense variant in the CPAMD8 gene in a patient with MCOR. We conducted a comprehensive clinical examination of a patient diagnosed with MCOR and performed whole-exome sequencing to identify potential pathogenic variants. Additionally, bioinformatics prediction tools were employed to assess the impact of the identified variant on protein structure and function. The patient presented with hallmark features of MCOR, such as bilaterally constricted pupils and a poor response to mydriatic agents. A novel homozygous nonsense variant, c.2679C>G (p.Tyr893*), was identified in the CPAMD8 gene. Protein modeling revealed that the variant results in complete truncation of the C-terminal domain of CPAMD8, disrupting its functional domains and potentially affecting its biological activity. Furthermore, electrostatic potential energy analysis demonstrated increased surface asymmetry of the protein, suggesting that the variant may interfere with protein-molecule interactions. Previous studies have suggested a strong association between MCOR and deletions in the 13q32.1 region of chromosome 13; however, the specific pathogenic genes involved have remained unclear. In this study, we show that the nonsense variant c.2679C>G (p.Tyr893*) in CPAMD8 is associated with MCOR, providing new insights into the genetic basis of the disease.

Congenital microcoria (MCOR) is a rare ocular anomaly characterized by pupil smaller than 2 mm with no response to mydriatic agents. It can present in two forms: autosomal recessive associated with Pierson syndrome and autosomal dominant isolated (associated with a high incidence of myopia and glaucoma). Studies have identified deletions in the 13q32.1 region of chromosome 13 that include the GPR180 gene, involved in smooth muscle cell growth, as the underlying cause. We describe 3 members of a family with deletion of the GPR180 gene on chromosome 13. In all, IOP was normal and gonioscopy showed iridocorneal angle dysgenesis with prominent ciliary processes. MCOR is due to poor development of the iris dilator muscle of genetic cause. Early diagnosis and continuous follow-up for possible complications such as amblyopia, progressive myopia and juvenile glaucoma is essential.

Congenital microcoria (MCOR) is a rare hereditary developmental defect of the iris dilator muscle frequently associated with high axial myopia and high intraocular pressure (IOP) glaucoma. The condition is caused by submicroscopic rearrangements of chromosome 13q32.1. However, the mechanisms underlying the failure of iris development and the origin of associated features remain elusive. Here, we present a 3D architecture model of the 13q32.1 region, demonstrating that MCOR-related deletions consistently disrupt the boundary between two topologically associating domains (TADs). Deleting the critical MCOR-causing region in mice reveals ectopic Sox21 expression precisely aligning with Dct, each located in one of the two neighbor TADs. This observation is consistent with the TADs' boundary alteration and adoption of Dct regulatory elements by the Sox21 promoter. Additionally, we identify Tgfb2 as a target gene of SOX21 and show TGFΒ2 accumulation in the aqueous humor of an MCOR-affected subject. Accumulation of TGFB2 is recognized for its role in glaucoma and potential impact on axial myopia. Our results highlight the importance of SOX21-TGFB2 signaling in iris development and control of eye growth and IOP. Insights from MCOR studies may provide therapeutic avenues for this condition but also for glaucoma and high myopia conditions, affecting millions of people.

Congenital microcoria has been extensively reported and usually leads to visual dysfunction or blindness. However, micropupil development secondary to cataract surgery has never been reported. Here, we describe a rare case of micropupil development in infancy that occurred secondary to combined cataract extraction and intraocular lens implantation for treatment of congenital cataract. When the patient reached adulthood, the affected eye not only gained good vision but also showed better ocular development and refractive status than the fellow eye. A 17-year-old boy presented to our outpatient clinic with decreased vision in his left eye related to congenital cataract surgery at 6 months of age. The affected eye had exhibited a pinhole pupil since the third month postoperatively. The condition had been managed with observation and regular monocular occlusion treatment. Upon presentation to our clinic, the best-corrected visual acuity (BCVA) in his fellow eye was 0.0 logMAR(20/20) with a refraction of - 5.75 diopters cylinder/-2.25 diopters sphere, and the BCVA in his affected eye was 0.5 logMAR(20/40) with a refraction of 0.00 diopters. Ophthalmic examination of the affected eye revealed a pinhole pupil (approximately 0.5 mm) with high light reflex sensitivity but no response to pupil-dilating drugs. The patient underwent pupilloplasty of the affected eye under corneal surface anesthesia. Postoperative examination revealed better ocular development in the affected eye than in the fellow eye (axial length: 24.21 vs. 27.02 mm, respectively) as well as better refractive status in the affected eye (BCVA of 0.0 logMAR(20/20) with a refraction of - 2.23 diopters cylinder/-3.00 diopters sphere vs. 0logMAR(20/20) with a refraction of -5.75 diopters cylinder/-2.25 diopters sphere). We have reported a rare case of micropupil development secondary to congenital cataract surgery, which is an uncommon complication, especially in children. However, unlike congenital microcoria, the secondary pinhole pupil may have reduced imaging haze and halos, possibly favoring the development of the affected eye. This case provides further insight into the treatment of congenital cataract.

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.