[Diffuse proliferative lupus nephritis in a patient with ulcerative colitis].

A 31 year-old man treated with sulfasalazine for ulcerative colitis, developed nephrotic syndrome, photosensitivity, alopecia, lymphopenia and hypocomplementemia. Anti-nuclear antibody (speckled) and antibodies to single-stranded DNA and SS-A were positive, while those against native DNA and histon were negative. Renal biopsy revealed diffuse proliferative lupus nephritis. His nephrotic syndrome partially improved with corticosteroid therapy combined with cessation of sulfasalazine. His complement level became normal, however it decreased again during the gradual reduction of corticosteroid dosage. In conclusion, we diagnosed the patient's illness as an idiopathic syntemic lupus erythematosus rather than sulfasalazine-induced lupus.