Can rs1420101 CT, rs20541 AG, and rs1801275 AG contribute to type 2 eosinophilic airway inflammation susceptibility?

Type 2 (T2) eosinophilic airway inflammation is a clinical inflammatory endotype, not a genotype-defined condition. In this 57-year-old man, rs1420101 CT, rs20541 AG, and rs1801275 AG can reasonably be viewed as susceptibility-related findings, but they cannot diagnose or exclude the phenotype.

Genetic and clinical evidence

• rs1420101 CT (IL1RL1) has the most coherent biomarker signal: carriage of the T allele has been associated in asthma cohorts, including Japanese-cohort replication, with higher blood eosinophil percentages and FeNO, as well as airway reversibility and lower FEV₁. However, these data do not establish a CT-specific risk estimate, and linkage disequilibrium limits assignment of causality to this SNP alone.
• rs20541 AG (IL13, Arg130Gln) carries an allele associated with higher total IgE and eosinophil counts and modest, population-dependent asthma susceptibility. Pooled AG-versus-GG evidence is nonsignificant or borderline, so it is not a robust individual predictor.
• rs1801275 AG (IL4Rα, R576) is biologically plausible, but direct human AG-specific evidence for a defined eosinophilic airway endotype remains uncertain; reported asthma associations vary by ancestry.

Mechanistic interpretation

• Reduced soluble ST2 associated with the rs1420101-linked IL1RL1 regulatory signal could lessen IL-33 sequestration, potentially increasing IL-33/ST2L-driven T2 activity.
• IL-4Rα R576 has experimental links to GRB2/ERK/IL-6/STAT3 signaling, increased IL-17 and IL-13, airway hyperresponsiveness, and eosinophilic inflammation in mice.

Clinical implications

• Bottom line: These variants may contribute to susceptibility, but none—alone or in combination—establishes T2 eosinophilic airway inflammation. Phenotyping requires clinical context plus biomarkers such as blood eosinophils (suggested indicator ≥150/µL), FeNO (≥20 ppb), and, where available, sputum eosinophils (≥2%), interpreted with treatment and comorbidities in mind.