The optimal cutoff values for diagnosing IPA were 238.7 pg/mL for BALF IFN-λ1 and 133.9 pg/mL for IFN-λ3, with sensitivities of 73.04% and 62.61%, and specificities of 78.35% and 73.16%, respectively. The gene discussed is IFNL1; the disease is Ito hypomelanosis.