Antinuclear Antibodies and Propylthiouracil Therapy

To the Editor.— Drugs that have been reported to activate systemic lupus erythematosus (SLE) can be divided into those that do so by their own pharmacologic properties, and thus cause it in a considerable percentage of individuals who receive them (hydralazine hydrochloride, isoniazid, procainamide hydrochloride, and various anticonvulsants), and drugs that apparently do it by causing allergic reactions which in turn trigger SLE.1 One common denominator of drugs that act on their own is that they elicit antinuclear antibodies (ANA) in an even larger percentage of individuals taking them on a long-term basis.2-4 Activation of SLE by propylthiouracil (PTU) has been described on at least three occasions.5-7These reports suggest that this drug might have lupus-activating properties of its own. We have, therefore, investigated the presence and specifity of ANA in the serum of 46 patients (34 females) undergoing long-term PTU treatment by means of a microcomplement