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.

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.

Clinical characteristics and genotype-phenotype correlation in 62 patients with X-linked agammaglobulinemia.

INTRODUCTION: X-linked agammagobulinemia (XLA) is a primary immunodeficiency disorder caused by Bruton's tyrosine kinase (Btk) gene mutation. Recent studies suggested genotype-phenotype correlation in XLA, but a definitive association remains controversial. PATIENTS AND METHODS: We examined the relationship between specific Btk gene mutations and severity of clinical presentation in 62 patients with XLA. Disease severity was assessed by the age of disease onset and the presence of severe infections, while mutations were classified into severe and mild based on structural and functional consequence by bioinformatics analysis. RESULTS: Fifty-six Btk mutations were identified in 62 patients from 57 kindreds. Variation in phenotypes was observed, and there was a tendency of association between genotype and age of disease onset as well as occurrence of severe infections. CONCLUSION: A critical analysis of the circumstances upon presentation also revealed that under-recognition of recurrent infections and relevant family history are important hurdles to timely diagnosis of XLA.

Susceptibility to mycobacterial infections in children with X-linked chronic granulomatous disease: a review of 17 patients living in a region endemic for tuberculosis.

BACKGROUND: Chronic granulomatous disease (CGD) is a rare disorder of phagocytic oxidative bursts leading to recurrent pyogenic infections. Affected individuals are most prone to infections caused by staphylococci, Salmonella, Candida, and Aspergillus, but previously we observed a high incidence of Mycobacterium tuberculosis infection in Chinese children with CGD. OBJECTIVE: To determine the spectrum of infections in patients with X-linked CGD, with an emphasis on mycobacterial infections, and to review all CYBB gene mutations identified in our center. RESULTS: From 1988 to 2005, 17 Chinese male children were diagnosed to have X-linked CGD. Fifteen mutations were identified, including 3 splice site defects (IVS1-1G>C, 266G>A, IVS3-1G>A), 5 missense mutations (591T>C, 627T>A, 949T>A, 1039T>A, 1512G>C), 3 nonsense mutations (882C>T, 1451C>A, 1569G>T), 1 insertion (756_757insA), and 3 deletions (660_662delTTC, 727delT, 1341delT). Eight of these were novel mutations. Recurrent pneumonia, lymphadenitis, and bacterial skin abscess were the commonest types of infection. Seven patients had tuberculosis (TB). Seven patients had prolonged scarring or abscess formation at the Calmette-Guérin bacillus (BCG) injection site, and 1 had disseminated BCG infection. Three patients had pulmonary aspergillosis. Four patients underwent hemopoietic stem cell transplantation, but 2 died of complications. CONCLUSIONS: Patients with CGD are susceptible to TB and BCG complications. Our observation suggests that oxidative burst is probably important in host defense against mycobacterial infections. Because interferon-gamma is the key cytokine involved in mycobacterial immunity, there may be a stronger indication for its use in CGD patients living in areas endemic for TB.

Modulating effects of mannose binding lectin genotype on arterial stiffness in children after Kawasaki disease.

Systemic arterial stiffness is increased in patients after Kawasaki disease (KD). Recently, associations between mannose-binding lectin (MBL) gene mutation and coronary complications in infants with KD and atherosclerosis in adults have been reported. We tested the hypothesis that MBL genotype modulates arterial stiffness in children after KD. Seventy-one KD patients (42 with and 29 without coronary aneurysms), aged 9.5 +/- 3.7 y, and 41 age-matched controls were studied. We determined and compared their blood pressure, brachioradial arterial stiffness as determined by pulse wave velocity (PWV), fasting total cholesterol, serum MBL level, and MBL genotype. Additionally, the modulating effects of different MBL expression genotypes [high level (HL) versus intermediate or low level (IL/LL)] on arterial stiffness in different groups were assessed. The MBL genotype distributions did not differ between patients and controls (p = 0.41) or between patients with and without coronary aneurysms (p = 0.42). Patients with IL/LL expression genotypes had significantly faster PWV than those with HL expression genotypes (7.93 +/- 1.38 m/s versus 6.67 +/- 2.28 m/s, p = 0.027). This genotype-modulating effect is more pronounced in patients without (HL 8.86 +/- 0.77 m/s versus IL/LL 6.48 +/- 2.32 m/s, p = 0.02) than those with (HL 7.50 +/- 1.41 m/s versus IL/LL 6.80 +/- 2.28 m/s, p = 0.32) coronary aneurysms. Multiple linear regression analysis identified age (beta = 0.26, p = 0.012), being a Kawasaki patient (beta = 0.22, p = 0.015), and MBL IL/LL genotype subgroup (beta = 0.20, p = 0.03) as significant determinants of arterial stiffness in the entire cohort. In conclusion, MBL genotype modulates arterial stiffness, an important cardiovascular risk factor, in children after KD.