Continuing this strategy, we investigated the following genes, which are responsible for 4 of the autoinflammatory hereditary periodic fever syndromes (HPFS): NLRP3 (CIAS1/cryopyrin/NALP3/PYPAF1), responsible for cryopyrin-associated periodic syndrome; NOD2 (CARD15), responsible for Blau syndrome; MEFV (marenostrin/pyrin), responsible for familial Mediterranean fever; and PSTPIP1 (CD2BP1/PSTPIP), responsible for pyogenic arthritis, pyoderma gangrenosum, and acne (PAPA) syndrome (4). The gene discussed is NOD2; the disease is bacterial arthritis.