In two distinct studies on sporadic PAs, Costa-Guda et al. [14,15] found inactivating germline and somatic mutations in four cyclin-dependent kinase inhibitor genes (CDKN1A, CDKN1B, CDKN2B and CDKN2C), encoding, respectively, the p21Cip1, p27Kip1, p15INK4b and p18INK4C inhibitors of the cyclin-dependent kinases, and negative regulators of cell cycle progression and cell proliferation. This evidence concerns the gene CDKN1B and gonorrhea.