Genetic characteristics of a family with Axenfeld-Rieger syndrome caused by 4q25 microdeletion

Objective  To investigate the clinical manifestations and genetic characteristics of a Chinese Han family with Axenfeld-Rieger syndrome (ARS).

Methods  A pedigree study was conducted.Three people from a Chinese Han family with ARS who visited Henan Eye Hospital in January 2024 were included, including 1 patient.Clinical data of the proband and her parents were collected.Comprehensive ophthalmic examination and general physical examination were performed on the proband and her parents.Peripheral blood samples were obtained from family members for DNA extraction.Whole exome sequencing was performed on the proband, and the copy number of the ZBED1P1, ENPEP, PITX2, and FAM241A genes in family members were validated using the real-time fluorescent quantitative PCR.Axenfeld-Rieger syndrome, Axenfeld-Rieger Syndrome, and PITX2 were used as keywords to search across databases such as OMIM, ClinVar, PubMed, CNKI, Wanfang, VIP, DECIPHER, and Google Scholar.The clinical manifestations and microdeletion types of different patients in ARS literature related to PITX2 microdeletions in China population were summarized, and the relationship between genotype and clinical phenotype was analyzed.The study followed the Declaration of Helsinki, and the study protocol was approved by the Ethics Committee of Henan Eye Hospital (No.HNEEC-2024[34]).All subjects understood the purpose of the study and voluntarily signed the informed consent form.

Results  The proband was a 25-year-old female, exhibiting diminutive cornea in both eyes, polycoria, deformation and displacement of pupils, a flat mid-face, maxillary dysplasia, tooth loss, and a protruding umbilicus, among other symptoms.Parents of the proband were phenotypically normal.DNA sequencing identified a 1.06 MB microdeletion on chromosome 4q25 in the proband.Real-time quantitative PCR confirmed that this microdeletion encompassed the PITX2 and ENPEP genes, and it was absent in the proband’s parents.The ClinGen CNV pathogenicity scoring indicated that the deletion involving the PITX2 gene represented a novel pathogenic copy number variation (CNV).Five studies related to 4q25 microdeletion in Chinese families with Axenfeld-Rieger syndrome was screened, including 13 patients.Clinical manefestations of the 13 patients included corneal disorders (accounting for 100%), umbilical hernia and dental anomalies (accounting for 92%), irregular intraocular pressure (accounting for 62%), iris atrophy (accounting for 46%), and posterior corneal embryotoxon (accounting for 31%).

Conclusions  For this Chinese family diagnosed with ARS, a novel pathogenic 4q25 microdeletion variant encompassing the PITX2 gene was found in the proband, which is associated with characteristic phenotypes including microcornea, congenital iris dysplasia, polycoria, tooth loss, and a protruding umbilicus.

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