Pneumocystosis is an opportunistic infection that occurs frequently in immunodeficient patients, mainly in those with the acquired immunological deficiency (AIDS). The authors report the case of a patient with insidious symptoms of fever, cough, and weight loss. Thorax radiography revealed a tumoral image in the right costophrenic angle. Treatment for tuberculosis (therapeutic test) presented no response. An open lung biopsy was performed and the histological examination revealed Pneumocystis carinii pneumonia. The patient presented significant clinical and radiological improvement with specific treatment.

Keywords: pneumocystis carinii pneumonia; AIDS-related opportunistic infections