Massive reversible pulmonary cysts in a patient with AIDS.

We report the case of a patient with AIDS who presented with bilateral, massive pulmonary cystic disease and pneumothorax presumably caused by Pneumocystis carinii which responded to treatment with cotrimoxazole. Follow-up with sequential chest X-rays and computed tomography scans showed a progressive improvement in the lung cysts which had resolved almost completely 11 months later. Several theories have been proposed to explain the cavitary lesions in this infection. The course observed in our patient suggests that a non-destructive mechanism was responsible for his lung cysts.