Background: Primary immunodeficiency diseases (PIDs) comprise more than 400 rare diseases with potential life-threatening conditions. Clinical manifestations and genetic defects are heterogeneous and diverse among populations. Here, we aimed to characterize the clinical, immunological and genetic features of Thai pediatric patients with PIDs. The use of whole exome sequencing (WES) in diagnosis and clinical decision making was also assessed. Methods: 36 unrelated patients with clinical and laboratory findings consistent with PIDs were recruited from January 2010 to December 2020. WES was performed to identify the underlying genetic defects. Results: The median age of disease onset was 4 months (range; 1 month to 13 years) and 24 were male (66.7%). Recurrent sinopulmonary tract infection was the most common clinical presentation followed by septicemia, and severe pneumonia. Using WES, we successfully identified the underlying genetic defects in 18 patients (50%). Of the 20 variants identified, six have not been previously described (30%). According to the International Union of Immunological Societies (IUIS), 38.9% of these detected cases (7/18) were found to harbor variants associated with genes in combined immunodeficiencies with associated or syndromic features (Class II). Conclusion: The diagnostic yield of WES in this patient cohort was 50%. Six novel genetic variants in PID genes were identified. The clinical usefulness of WES in PIDs was demonstrated, emphasizing it as an effective diagnostic strategy in these genetically heterogeneous disorders.

Background: The incidence of allergic diseases has been rising in the last decades. The interplay between genetic and environmental factors underlined these complex diseases. Data concerning natural history and risk factors associated with allergic diseases in developing Asian countries are limited. Methods: A population-based birth cohort study was conducted in Bangkok, Thailand. Perinatal and postnatal factors were prospectively collected by questionnaires. Sensitization was identified by skin prick test. Food allergy (FA) was confirmed by oral food challenge. Results: A total of 369 mother-children pairs were enrolled and follow-up until the age of 30 months. The cumulative incidence of allergic diseases was 46.2%. High family income significantly increased risk of atopic dermatitis (AD) and ever-wheezing. Maternal history of allergic diseases and exclusive breastfeeding longer than six months significantly increased risk of FA. Antibiotics use in infants significantly associated with FA, ever-wheezing and rhinitis. Infants with FA had a 6.5-fold increased risk of AD while infants with AD had an 8.5-fold increased risk of FA. AR had a 3.5-fold increased risk in developing ever-wheezing. One-third of the subjects had aeroallergen sensitization. Conclusion: Prevalence of allergic diseases in developing Asian country was considerably high. AD and FA were the most prevalent allergic diseases during the first years of life. Meanwhile, the prevalence of wheezing and rhinitis subsequently increased over time. High sensitization rate to aeroallergens was found in the first two years of life. Maternal atopy, high family income, early life exposure to antibiotics and prolonged breast-feeding increased risk of allergic diseases in our cohort.