CD63 and pachyonychia congenita: SRM analysis revealed that 45 out of the 64 proteins were significantly altered between low-grade (n = 22, GS ≤ 3 + 4) and high grade PC (n = 31) [57], with the best performance obtained for the combination of 5 proteins (Prostatic acid phosphatase, PSA, CD63 antigen (CD63), N-sulphoglucosamine sulphohydrolase, and Putative glycerol kinase 5) reaching an AUC of 0.70 [57].