Pneumocystis carinii infection of the thyroid gland has previously been described in only four living patients with acquired immunodeficiency syndrome, three of whom had been receiving inhaled pentamidine prophylaxis against P carinii pneumonia. We treated three additional patients with P carinii thyroid involvement, all of whom were receiving aerosolized pentamidine. Two of our patients presented with clinical features suggestive of subacute granulomatous thyroiditis. The diagnosis of P carinii in our patients, as well as in the previously described patients, was established by thyroid fine-needle aspiration and Gomori's silver methenamine stains. The recent emergence of P carinii infection of the thyroid gland is likely related to the use of inhaled pentamidine prophylaxis, which appears to predispose to the development of extrapulmonary pneumocystosis. Clinicians need to be aware of the possibility of P carinii thyroiditis and should use aspiration and Gomori's methenamine silver staining in studying patients with the acquired immunodeficiency syndrome who have a painful (or other unexplained) thyroid mass so as to be able to initiate prompt and appropriate therapy.
(Arch Intern Med. 1993;153:393-396)