Notably, in eight cases (cases 2, 4, 6, 7, 10, 11, 12, and 13), the increase in KL-6 during immunosuppressive treatment was attributed to the exacerbation of IP rather than the onset of PAP, leading to intensified immunosuppressive treatment and subsequent exacerbation of PAP. Here, MUC1 is linked to incontinentia pigmenti.