Clinical features and mutational analysis of X-linked agammaglobulinemia patients in Malaysia.

Background: Bruton's tyrosine kinase (BTK) is a cytoplasmic protein involved in the B cell development. X-linked agammaglobulinemia (XLA) is caused by mutation in the BTK gene, which results in very low or absent B cells. Affected males have markedly reduced immunoglobulin levels, which render them susceptible to recurrent and severe bacterial infections. Methods: Patients suspected with X-linked agammaglobulinemia were enrolled during the period of 2010-2018. Clinical summary, and immunological profiles of these patients were recorded. Peripheral blood samples were collected for monocyte BTK protein expression detection and BTK genetic analysis. The medical records between January 2020 and June 2023 were reviewed to investigate COVID-19 in XLA. Results: Twenty-two patients (from 16 unrelated families) were molecularly diagnosed as XLA. Genetic testing revealed fifteen distinct mutations, including four splicing mutations, four missense mutations, three nonsense mutations, three short deletions, and one large indel mutation. These mutations scattered throughout the BTK gene and mostly affected the kinase domain. All mutations including five novel mutations were predicted to be pathogenic or deleterious by in silico prediction tools. Genetic testing confirmed that eleven mothers and seven sisters were carriers for the disease, while three mutations were de novo. Flow cytometric analysis showed that thirteen patients had minimal BTK expression (0-15%) while eight patients had reduced BTK expression (16-64%). One patient was not tested for monocyte BTK expression due to insufficient sample. Pneumonia (n=13) was the most common manifestation, while Pseudomonas aeruginosa was the most frequently isolated pathogen from the patients (n=4). Mild or asymptomatic COVID-19 was reported in four patients. Conclusion: This report provides the first overview of demographic, clinical, immunological and genetic data of XLA in Malaysia. The combination of flow cytometric assessment and BTK genetic analysis provides a definitive diagnosis for XLA patients, especially with atypical clinical presentation. In addition, it may also allow carrier detection and assist in genetic counselling and prenatal diagnosis.

Burden of pertussis among young infants in Malaysia: A hospital-based surveillance study.

BACKGROUND: The case fatality rate and the risk of complications due to pertussis is very high in infants. Asia has the second highest childhood pertussis burden. The study aimed to assess the prevalence, clinical complications, and mortality rates of pertussis disease requiring hospitalization among young infants in Malaysia. METHODS: The study was a one-year, hospital-based, multi-site surveillance of infants less than six months of age with symptoms consistent with pertussis and a cross-sectional analysis of their mothers for recent pertussis infection. Information was obtained from medical records and interviews with the parents. Pertussis diagnosis was confirmed for all infants through serum anti-PT titration test or PCR test. RESULTS: 441 possible cases of pertussis were included in this study. Of these, 12.7 % had laboratory confirmation of pertussis. Infants with confirmed pertussis had significantly higher rates of cyanosis (37.5 % vs 8.6 %; p < 0.0001) and apnea (12.5 % vs 3.9 %; p = 0.027) than test-negative infants. Most infants from both groups were in recovery/recovered at discharge. Those with confirmed pertussis had higher case fatality rate than test-negative cases (5.4 % vs 1.0 %; p = 0.094), but the difference did not reach significance. The majority of confirmed pertussis cases (89.3 %) occurred in infants too young to be fully vaccinated or under-vaccinated for their age. Both test-negative and confirmed pertussis resulted in work-day losses and incurred costs for both parents. CONCLUSIONS: A high pertussis disease burden persists in infants less than six months of age, especially among those un- and under-vaccinated. Maternal and complete, on-time infant vaccination is important to reduce disease burden.

A single-center pilot study in Malaysia on the clinical utility of whole-exome sequencing for inborn errors of immunity.

Primary immunodeficiency diseases refer to inborn errors of immunity (IEI) that affect the normal development and function of the immune system. The phenotypical and genetic heterogeneity of IEI have made their diagnosis challenging. Hence, whole-exome sequencing (WES) was employed in this pilot study to identify the genetic etiology of 30 pediatric patients clinically diagnosed with IEI. The potential causative variants identified by WES were validated using Sanger sequencing. Genetic diagnosis was attained in 46.7% (14 of 30) of the patients and categorized into autoinflammatory disorders (n = 3), diseases of immune dysregulation (n = 3), defects in intrinsic and innate immunity (n = 3), predominantly antibody deficiencies (n = 2), combined immunodeficiencies with associated and syndromic features (n = 2) and immunodeficiencies affecting cellular and humoral immunity (n = 1). Of the 15 genetic variants identified, two were novel variants. Genetic findings differed from the provisional clinical diagnoses in seven cases (50.0%). This study showed that WES enhances the capacity to diagnose IEI, allowing more patients to receive appropriate therapy and disease management.

Atypical Presentation of Severe Fungal Necrotizing Fasciitis in a Patient with X-Linked Agammaglobulinemia.

X-linked agammaglobulinemia is a rare primary immunodeficiency due to a BTK mutation. The patients are characteristically deficient in peripheral B cells and serum immunoglobulins. While they are susceptible to infections caused by bacteria, enteroviruses, and parasites, fungal infections are uncommon in XLA patients. Here, we report a boy of Malay ethnicity who suffered from recurrent upper respiratory tract infections and severe progressive necrotizing fasciitis caused by Saksenaea erythrospora. Immunological tests showed a B cell deficiency and hypogammaglobulinemia. Whole-exome sequencing identified a dinucleotide deletion (c.1580_1581del) in BTK, confirmed by Sanger sequencing and predicted to be disease causing by in silico functional prediction tools (Varsome and MutationTaster2) but was absent in the gnomAD database. This mutation resulted in a frameshift and premature termination (p.C527fs), which disrupted the protein structure. The mother was heterozygous at the mutation site, confirming her carrier status. Flow cytometric analysis of monocyte BTK expression showed it to be absent in the patient and bimodal in the mother. This study describes a novel BTK mutation in a defined hotspot and an atypical fungal phenotype in XLA. Further studies are required to understand the pathogenesis of fungal infection in XLA.

A novel de novo NLRC4 mutation reinforces the likely pathogenicity of specific LRR domain mutation.

Autoinflammatory disorders are characterized by dysregulated innate immune response, resulting in recurrent uncontrolled systemic inflammation and fever. Gain-of-function mutations in NLRC4 have been described to cause a range of autoinflammatory disorders. We report a twelve-year-old Malay girl with recurrent fever, skin erythema, and inflammatory arthritis. Whole exome sequencing and subsequent bidirectional Sanger sequencing identified a heterozygous missense mutation in NLRC4 (NM_001199138: c.1970A > T). This variant was predicted to be damaging in silico, was absent in public and local databases and occurred in a highly conserved residue in the leucine-rich repeat (LRR) domain. Cytokine analysis showed extremely high serum IL-18 and IL-18/CXCL9 ratio, consistent with other NLRC4-MAS patients. In summary, we identified the first patient with a novel de novo heterozygous NLRC4 gene mutation contributing to autoinflammatory disease in Malaysia. Our findings reinforce the likely pathogenicity of specific LRR domain mutations in NLRC4 and expand the clinical spectrum of NLRC4 mutations.

Incidence and predictors of severe anemia in Asian HIV-infected children using first-line antiretroviral therapy.

BACKGROUND: There are limited data on treatment-related anemia in Asian HIV-infected children. METHODS: Data from Asian HIV-infected children aged <18 years on first-line highly active antiretroviral therapy (HAART) were used. Children who had pre-existing severe anemia at baseline were excluded. Anemia was graded using the United States Division of AIDS (DAIDS) 2004 table. Potential risk factors for severe anemia were assessed by logistic regression. RESULTS: Data from 1648 children (51.9% female, 62.8% World Health Organization (WHO) stage 3/4) were analyzed. Median (interquartile range) age was 6.8 (3.7-9.6) years, CD4% was 9 (3-16)%, and plasma HIV-RNA was 5.2 (4.7-5.6) log10 copies/ml at HAART initiation in those with available testing. The most common regimens were stavudine/lamivudine/nevirapine (42%) and zidovudine/lamivudine/nevirapine (25%). Severe anemia was identified in 47 (2.9%) children after a median time of 6 months after HAART initiation, with an incidence rate of 5.4 per 100 child-years. Mild anemia or moderate anemia at baseline (p = 0.024 and p = 0.005, respectively), previous or current use of zidovudine (p < 0.0001 and p = 0.013, respectively), and male sex (p = 0.008) were associated with severe anemia. Higher weight-for-age z-score (p = 0.004) was protective. CONCLUSIONS: The incidence of severe anemia in Asian HIV-infected children after HAART initiation was low and mainly occurred during the first few months after HAART initiation. Mild to moderate anemia at baseline and using zidovudine were independent risk factors for the development of severe anemia.