TNF and inflammatory bowel disease: In total, 58 cases of PG without IBD treated with anti-TNF-α have been reported in the literature, of which 41% were idiopathic PG, 17% were associated with rheumatoid arthritis, 10% were post-surgical/traumatic, 7% were associated with hidradenitis suppurativa, 4% were associated with monoclonal gammopathy, and 3.5% were related to cocaine use (levimasol) [32].