B-306 DiGeorge Syndrome Associated With 10p Deletion: A Cytogenetic Case Report

Abstract

DiGeorge Syndrome (DGS) is a rare genetic disorder classically associated with the deletion of the long arm of chromosome 22, leading to craniofacial and cardiac malformations, hypoparathyroidism, and immunodeficiency. However, rare cases with similar phenotypes have been associated with deletions involving the terminal deletion of the short arm of chromosome 10, known as DGS2. These atypical cytogenetic findings highlight the importance of comprehensive chromosomal evaluation in suspected cases. The aim of this study was to report a case of DiGeorge syndrome associated with a deletion of the short arm of chromosome 10, supported by laboratory diagnostic evidence. A 1-year-old male patient with a clinical suspicion of DiGeorge Syndrome was referred for cytogenetic investigation in a large-scale Brazilian clinical laboratory and no other relevant clinical or phenotypic data were provided. Cytogenetic analysis was performed by conventional karyotyping using a peripheral blood sample collected in a heparinized tube. For this purpose, a 72-hour culture with T-cell mitogen and cellular processing was performed according to the AGT Cytogenetics Laboratory Manual. The obtained metaphases were analyzed according to technical criteria and the nomenclature standardized by the International System for Human Cytogenomic Nomenclature (ISCN), ensuring proper interpretation and description of the chromosomal findings. G-banded karyotyping analysis revealed an interstitial deletion of the short arm of chromosome 10: 46,XY,del(10)(p13p14). Although rare, chromosome 10 deletions are described in the literature, resulting in a variable phenotype that may be associated with DGS. The deletion identified in the patient encompasses the DGS2 gene locus located at band 10p13-p14. Among chromosome 10 alterations, the 10p13 deletion is the most common associated with DGS, referred to as DGS2, presenting a clinical picture similar to the classic 22q11 deletion. Despite the lack of the patient's clinical data, completing questionnaires during genetic testing requests is fundamental to guide the analysis and report drafting, serving as important tools for clinical-laboratory decision-making. Furthermore, knowing the associated phenotypes, syndromes, and their variants optimizes diagnostic assertiveness and accuracy, as alterations close to the 5 Mb resolution limit may go unreported. In the context of DGS, the karyotype plays an essential role in the better characterization of the syndrome and its variants, given that 10p chromosome deletions can involve approximately 7 Mb of genomic material, and the technique allows for the detection of any alteration larger than 5 Mb. This case report reinforces the importance of cytogenetic analysis in identifying atypical chromosomal alterations in patients with suspected DiGeorge syndrome. Recognition of 10p deletions expands the genetic spectrum of the syndrome and emphasizes the importance of considering alternative loci when the 22q11 deletion is absent These findings underscore the role of conventional karyotyping in accurate laboratory diagnosis in rare cases, making it an essential tool for clinical management and genetic counseling.