Two patients had pyoderma gangrenosum and rheumatoid arthritis. Biopsy specimens of the cutaneous ulcers in the patients showed a necrotizing vasculitis. Complement (C3) and immunoglobulins were not detected in the skin lesions. There was no important impairment of cell-mediated immunity observed.
Stolman LP, Rosenthal D, Yaworsky R, Horan F. Pyoderma Gangrenosum and Rheumatoid Arthritis. Arch Dermatol. 1975;111(8):1020-1023. doi:10.1001/archderm.1975.01630200080009