Pneumocystis carinii infection presenting as an intra-abdominal cystic mass in a child with acquired immunodeficiency syndrome.

We describe the case of a pediatric patient with acquired immunodeficiency syndrome (AIDS) with an unusual large, fluid-filled intra-abdominal cystic lesion in which Pneumocystis carinii trophozoites were identified. Extrapulmonary P. carinii infection should be considered in the differential diagnosis of an intra-abdominal cystic mass in a child with AIDS.