Targeted Gene Sanger Sequencing Should Remain the First-Tier Genetic Test for Children Suspected to Have the Five Common X-Linked Inborn Errors of Immunity

Abstract

To address inborn errors of immunity (IEI) which were underdiagnosed in resource-limited regions, our centre developed and offered free genetic testing for the most common IEI by Sanger sequencing (SS) since 2001. With the establishment of The Asian Primary Immunodeficiency (APID) Network in 2009, the awareness and definitive diagnosis of IEI were further improved with collaboration among centres caring for IEI patients from East and Southeast Asia. We also started to use whole exome sequencing (WES) for undiagnosed cases and further extended our collaboration with centres from South Asia and Africa. With the increased use of Next Generation Sequencing (NGS), we have shifted our diagnostic practice from SS to WES. However, SS was still one of the key diagnostic tools for IEI for the past two decades. Our centre has performed 2,024 IEI SS genetic tests, with in-house protocol designed specifically for 84 genes, in 1,376 patients with 744 identified to have disease-causing mutations (54.1%). The high diagnostic rate after just one round of targeted gene SS for each of the 5 common IEI (X-linked agammaglobulinemia (XLA) 77.4%, Wiskott–Aldrich syndrome (WAS) 69.2%, X-linked chronic granulomatous disease (XCGD) 59.5%, X-linked severe combined immunodeficiency (XSCID) 51.1%, and X-linked hyper-IgM syndrome (HIGM1) 58.1%) demonstrated targeted gene SS should remain the first-tier genetic test for the 5 common X-linked IEI.

Genetically confirmed chronic granulomatous disease in a Kenyan child: case report

“…Through this next-generation sequencing technique, they achieved a molecular diagnosis in 30% of the patients ( 33 ). Recently, the Asian Primary Immunodeficiency Network proposed targeted gene Sanger sequencing as the first-tier genetic test for children suspected to have the five common X-linked IEI: X-linked agammaglobulinemia, Wiskott–Aldrich syndrome, X-linked CGD, X-linked severe combined immunodeficiency, and X-linked hyper-IgM syndrome ( 34 ). The optimal approach to the choice of genetic testing for CGD and other IEI will need to be contextualized.…”

Co-Occurring X-Linked Agammaglobulinemia and X-Linked Chronic Granulomatous Disease: Two Isolated Pathogenic Variants in One Patient

“…X-linked agammaglobulinemia (XLA) and X-linked chronic granulomatous disease (XCGD) are two of the five most common X-linked immunodeficiencies, both often diagnosed via single- or multi-gene Sanger sequencing despite the rapidly increasing use of next-generation sequencing [ 1 ]. Disregarding a shared location on the X chromosome, the diseases themselves are distinct: XLA is an antibody deficiency syndrome caused by mutations in the Bruton tyrosine kinase ( BTK ) gene leading to deficiency of mature B lymphocytes, agammaglobulinemia, and susceptibility to infection [ 1 , 2 ]. Immunoglobulin replacement continues to be the cornerstone of treatment, with improved outcomes in cases of early diagnosis and treatment initiation [ 3 ].…”