Potassium iodide sensitivity in four patients with hypocomplementemic vasculitis.

During metabolism studies of radiolabeled proteins in 126 participants four patients were suspected of being sensitive to potassium iodide (Kl) because they repeatedly developed urticaria and other symptoms after Kl administration. Two of the four patients suspected of Kl sensitivity and 10 control patients were orally challenged with Kl to document and characterize Kl sensitivity and to evaluate the possible association(s) of Kl sensitivity with urticaria, hypocomplementemia, and vasculitis. The Kl challenges in the two sensitive patients precipitated urticaria, angioedema, polymyalgias, conjunctivitis, and coryza. One of these two patients also developed a severe systemic illness characterized by fever, headache, peritonitis, episcleritis, and pneumonitis. The four sensitive patients were strikingly similar in that they exhibited hypocomplementemia and dermal vasculitis associated with chronic urticaria or systemic lupus erythematosus, suggesting that other patients with similar clinical features may be sensitive to Kl and that Kl may precipitate severe systemic illness in them.