ULBP2 and pachyonychia congenita: We found that the serum levels of ULBP2, but not BIGH3, were significantly elevated in PC patients compared to those in the healthy controls: 1.87±1.67 versus 1.29±0.49 μg/mL for BIGH3 (p = 0.328; Fig. 3A) and 200.2±168.6 versus 51.4±64.6 pg/mL for ULBP2 (p<0.0001; Fig. 3B).