We performed a retrospective medical chart review of 19 patients diagnosed with CIU and subsequently treated with sulfasalazine at Johns Hopkins Bayview Medical Center, Baltimore, Md, from 2002 to 2005. The study was approved by the institutional review board at the Johns Hopkins Medical Institutions, Baltimore. The diagnosis of CIU was based on clinical history and physical examination and was supported by skin biopsy findings in 17 cases (89%). The remaining 2 patients did not have any biopsy data on record and were diagnosed as having CIU solely on their disease presentation. The following information was obtained: disease duration, history of angioedema, presence of thyroid autoantibodies (antimicrosomal and antithyroglobin), thyroid function, dosage of sulfasalazine therapy, subjective clinical response to sulfasalazine therapy, adverse effects during sulfasalazine therapy, therapies for CIU used before and after sulfasalazine therapy, and skin biopsy findings. Before the initiation of sulfasalazine therapy, baseline blood work, including kidney and liver function tests, a complete blood cell count, and determination of thyrotropin and antimicrosomal and antithyroglobin antibodies, was performed. A punch biopsy of an urticarial wheal was performed to rule out other diagnoses such as urticarial vasculitis and to further characterize the urticaria as lymphocyte or neutrophil predominant. Patients were counseled on the potential adverse effects of sulfasalazine, including headache, photosensitivity, gastrointestinal distress, liver and kidney abnormalities, leukopenia, and reversible oligospermia. The sulfasalazine therapy was started at a dosage of 500 mg/d and increased by 500 mg each week until a satisfactory clinical response was achieved or until a daily dose of 2 to 4 g/d was reached. During dose escalation, blood work was repeated weekly and then every 3 months after the final dosage had been reached.