KLK3 and pachyonychia congenita: This is in agreement with reports showing that O-linked β-N-acetylglucosaminylation levels in PC tissues were correlated with a higher GS and a poorer prognosis [60] and that increased levels of α2-3-linked sialic acid on serum glycoproteins in PC patients can enhance the specificity and sensitivity in predicting GS when compared with PSA [61].