CTSC and Papillon-Lefevre disease: Eick et al. compared the levels of LL-37 in GCF, saliva, and neutrophil-derived enzymes, which revealed the fact that dysfunctional cathepsin C in patients of Papillon-Lefevre syndrome caused the deficit in immunomodulatory and antimicrobial functions of LL-37 in GCF, leading to severe periodontal disease.