Pyogenic sterile arthritis, pyoderma gangrenosum, and acne (PAPA) syndrome is a rare autoimflammatory disease with early onset, developing erosive arthritis. It is inherited in an autosomal dominant fashion. Patients typically develop cystic acne, abscesses and cutaneous ulcers, including pyoderma gangrenosum-like lesions. PAPA syndrome is caused by gain-of function mutations in PSTPIP1, a protein capable of associating with pyrin. Mutated PSTPIP1 reduces the inhibitory role of pyrin on inflammasome activation and therefore, potentiates the IL-1beta pathway. Elevated TNFalpha levels are also described.
