Potassium Iodide and Vasculitis

To the Editor.—  The systemic and cutaneous effects of oral potassium iodide remain an enigma. Horio et al (Archives 1981;117:29-31) reported the beneficial effects of potassium iodide in the therapy for erythema nodosum and nodular vasculitis. Not only are the pathophysiologic characteristics of this response unknown, but they allude to occasional induction of vasculitis and erythema nodosum by iodides. Before dermatologists embark on therapeutic programs of potassium iodide for vasculitis, a note of caution should be stressed.Curd and co-workers¹ have recently reported four cases with hypocomplementemia and dermal vasculitis in which potassium iodide administration was variably associated with urticaria, angioedema, polymyalgia, and life-threatening systemic illness. They suggest that hypocomplementemia and dermal vasculitis may serve as a clinical marker for such severe potassium iodide reactions. In addition, there are reports of periarteritis nodosa precipitated by potassium iodide administration.^2,3How, then, are we to judge when the administration of