Pneumocystis pneumonia in a patient with normal chest roentgenograms and normal arterial blood gas values.

For unknown reasons, manifestations of even heavy opportunistic infection in AIDS patients may be chronic and subtle. We have presented the second fully reported case of an AIDS patient with symptomatic Pneumocystis carinii pneumonia in whom the usual screening tests of blood gases and chest roentgenography were normal to all observers. Diffusing capacity for carbon monoxide can be an early and sensitive indication of PCP.