ĐẶC ĐIỂM SỐ LƯỢNG BẢN SAO TREC VÀ KREC Ở BỆNH NHI RỐI LOẠN MIỄN DỊCH BẨM SINH

Abstract

Background: Quantification of T-cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC) reflects newly generated T and B lymphopoiesis in the thymus and bone marrow and is commonly applied in newborn screening for severe immunodeficiency. However, data regarding the value of these markers in pediatric patients with Inborn Errors of Immunity (IEI) in Vietnam remain limited, particularly in relation to circulating mature lymphocyte subsets in peripheral blood.

Objective: To describe TREC and KREC levels and their association with peripheral blood lymphocyte subsets (CD3, CD4, CD8, CD19) in pediatric patients with IEI.

Methods: A cross-sectional descriptive study was conducted in 24 pediatric patients diagnosed with IEI who were treated and followed at the Hematology-Dengue Department, Children’s Hospital 1, from June 2025 to February 2026.

Results: The male-to-female ratio was 1:1, and the 1-6 year age group accounted for the highest proportion. Infection was the most common clinical manifestation (58.3%). IEI categories directly affecting lymphocyte development and function (groups 1-3 according to the 2024 IUIS classification) accounted for 58.3% of cases. Reduced TREC levels were observed in 92.8% of patients in groups 1-3 and in 80% of patients in the remaining groups. Reduced KREC levels were identified in 50% of patients in groups 1-3 and in 70% of patients in other groups. In most cases, TREC and KREC levels were concordant with peripheral lymphocyte subsets (CD3, CD4, CD8, CD19), showing either simultaneous reduction or normal values. However, 37.5% of cases demonstrated reduced TREC and/or KREC despite lymphocyte counts remaining within age-adjusted reference ranges, suggesting the potential for early detection of impaired lymphopoiesis before a marked decline in circulating lymphocytes. This discordance was also observed in some patients with autoimmune manifestations who belonged to IEI groups not directly associated with classical lymphocyte developmental defects.

Conclusion: TREC and KREC reflect abnormalities in lymphocyte generation in pediatric IEI, including cases outside classical lymphopoietic disorders. Reduced TREC and/or KREC may occur even when peripheral blood lymphocyte counts remain within age-adjusted reference ranges and were also observed in some patients with autoimmune manifestations. The combined assessment of TREC, KREC, and lymphocyte subsets may support evaluation of lymphopoietic impairment in clinical practice and warrants further investigation regarding the role of these markers.