Pneumocystis carinii infection of the thyroid in a hypothyroid patient with AIDS: diagnosis by fine needle aspiration biopsy.

A 49-yr-old homosexual man with acquired immunodeficiency syndrome presented with a left-sided neck mass. He was found to have a firm goiter. He was clinically euthyroid, but had laboratory evidence of primary hypothyroidism. Radioactive iodine scan of the thyroid showed homogeneous uptake over an enlarged right lobe and absence of uptake over the left lobe. Two fine needle aspiration biopsies of the thyroid revealed the presence of Pneumocystis carinii (P. carinii) organisms on the Gomori's methenamine silver strain. After courses of iv and oral therapy with trimethoprim-sulfamethoxazole, a third fine needle aspiration biopsy failed to reveal any organisms. A repeated radioactive iodine scan of the thyroid showed return of uptake over the left lobe. Thyroid function tests normalized with levothyroxine, and the goiter decreased in size. To our knowledge, this is the first report of hypothyroidism associated with P. carinii infection of the thyroid. P. carinii infection should be considered in the differential diagnosis of human immunodeficiency virus infected individuals presenting with cold thyroid nodules. Fine needle aspiration biopsy is a valuable tool in assessing these patients.