The optimal cutoff value of BALF PTX3 for diagnosing IPA was 2.67 ng/ml, with an area under the curve (AUC) of 0.84 (95% CI, 0.80-0.89), sensitivity of 85.57% (95% CI, 77.22-91.20), and specificity of 71.72% (95% CI, 66.28-76.60). The gene discussed is PTX3; the disease is Ito hypomelanosis.