CTSC and Haim-Munk syndrome: In cathepsin C-deficient mice, the function of the cytotoxic T cells is impaired (Pham and Ley, 1999) whereas in humans, defects in the cathepsin C gene are associated with Papillon-Lefevre disease, Haim-Munk syndrome (Sulák et al., 2016) and aggressive periodontitis (Nagy et al., 2014).