Pneumocystis carinii thyroiditis.

A 38-year-old black man with a history of acquired immunodeficiency syndrome associated with intravenous drug abuse presented with two weeks of left-sided neck swelling. Results of thyroid function tests were within normal limits. Thyroid scan demonstrated nonvisualization of the left lobe. Fine-needle aspiration of the thyroid revealed the presence of Pneumocystis carinii organisms in the thyroid tissue. Although chest radiography and computerized tomography of the chest detected several nodules and cavitary lesions, the results of bronchoalveolar lavage and transbronchial biopsy were negative for P. carinii. The patient showed a response to treatment with trimethoprim/sulfamethoxazole. Thyroidal involvement with P. carinii has previously been documented only in the setting of overwhelming, fatal pulmonary infection. The current case expands the clinical spectrum of extrapulmonary pneumocystosis and documents its successful treatment.