Furthermore, it has also been reported that serum KL-6 levels in SPAP are as high as in APAP [18]. In seven of the 14 cases in Table 1, the serum KL-6 levels before the diagnosis of PAP exceeded 2,050 U/mL, an atypically high level for IP. Here, PDZK1IP1 is linked to incontinentia pigmenti.