The serum KL-6 levels (832.0 ± 701.2 vs. 437.2 ± 480.3 U/mL; P < 0.001) and SP-D levels (141.0 ± 91.0 vs. 62.6 ± 47.6 U/mL; P = 0.005) were higher in ED-SCLC patients with IP than in those without IP. This evidence concerns the gene MUC1 and incontinentia pigmenti.