Eight out of nine patients (88.9%) with Bird-HP showed greater increases in serum KL-6 concentrations in the winter compared to the summer; as such, Smax-Wmax in patients with Bird-HP showed negative values and Smax-Wmax or Smax/Wmax was significantly lower than the other ILD (Table 1, Figure 2A). This evidence concerns the gene MUC1 and interstitial lung disease.