There is now evidence of mutations to the PSTPIP1 gene in cases of pyoderma gangrenosum, acne and suppurative hidradenitis (PASH) and pyogenic arthritis, pyoderma gangrenosum, acne and suppurative hidradenitis (PAPASH) syndromes (19, 24). Here, PSTPIP1 is linked to arthritic joint disease.