Compared to the patients with late-onset asthma, patients with early-onset asthma exhibited a higher median level of serum IL-17 [52.96(47.99, 105.50) vs. 44.75(20.81, 54.99) ng/L, P = 0.016] (shown in Fig. 1), and a higher neutrophils percentage in induced sputum samples (72.04 ± 26.90 vs. 53.61 ± 27.89%, P = 0.033). This evidence concerns the gene IL17A and asthma.