Novel Missense DNA Variants in the IL2RG Gene Identified in Slovak X-linked Severe Combined Immunodeficiency Disease Patients: A Case Report

Abstract

X-linked severe combined immunodeficiency disease (X-SCID) is a form of inborn errors of immunity (IEI) associated with causal DNA variants of the IL2RG gene. Patients with X-SCID are characterized by a combination of cellular and humoral immunodeficiencies associated with increased susceptibility to infections. The presented cases constituted two unrelated male patients from the Slovak population. Proband A was primarily hospitalized at the age of three months because of recurrent fever, vomiting, and lethargy, and the atypical immunophenotype was determined to be T-B-NK-. For proband B, the first hospitalization occurred at the age of eight months because of generalized impetiginized dermatitis. Whole exome sequencing (WES) was performed via a comprehensive approach in patients with undefined IEI, and causal DNA variants were confirmed by Sanger sequencing. WES analysis in probands identified the currently undescribed hemizygous variants p.Asn84Thr and p.Val213Ala in the IL2RG gene. Segregation analysis of p.Asn84Thr indicated a de novo origin, and p.Val213Ala was detected only in the asymptomatic proband's mother. We comprehensively reconsidered and scored both variants based on biological and clinical aspects. Finally, taking all the information into account, we classified p.Asn84Thr as likely pathogenic and p.Val213Ala as likely pathogenic with mild penetrance based on the fulfilled ACMG (American College of Medical Genetics and Genomics) criteria for computational predictions, clinical correlations, localization at functional site, and de novo status. With the WES approach, we identified two novel, not yet reported, IL2RG variants in the Slovak population of X-SCID patients. These findings strengthen the fact that rapid and comprehensive molecular-genetic diagnostics of IEI is necessary for the early definition of precise diagnosis, which further enables appropriate treatment and patient management.