An acute interstitial plasma cell pneumonia caused by Pneumocystis carinii, an organism currently categorized as a fungus.

Infection from Pneumocystis carinii, which can reside harmlessly in normal lungs, may occur when the body's defenses are immunocompromised and weakened by disease or medications, such as cancer and cancer treatments. It is a common opportunistic infection of acquired immunodeficiency syndrome (AIDS). More than 80 percent of individuals with AIDS develop pneumocystis pneumonia when standard treatments have not been implemented. Often, pneumocystis pneumonia is the first indication that a person with human immunodeficiency virus (HIV) (see Diagnostic Code: 6351 HIV-Related illness) infection has developed AIDS.

Symptoms may develop over several weeks. Fever, shortness of breath that may become severe, nonproductive cough, tachypnea, dyspnea, fatigue, and hypoxemia are common symptoms. Interstitial infiltrates may be seen with x-rays.

Physical examination and auscultation with a stethoscope, chest x-ray, sputum cultures, bronchoalveolar lavage, tissue biopsy, and blood studies may be valuable in diagnosing and identifying the causative organism. Computed tomography (CT) scan of the chest may be useful in complicated infections.

Trimethoprim-sulfamethoxazole (Bactrim) given by mouth is the usual antibiotic used in the treatment of pneumocystis carinii. It may be given intravenously with prednisone for severe infection and those with low blood oxygen levels. Alternative drug treatments may include clindamycin phosphate (CleocinT), primaquine phosphate, and pentamidine isethionate (Pentan).

Side effects of antibiotics are particularly common in people with AIDS. The death rate may range from 10 to 30 percent following treatment. Individuals with AIDS treated successfully for pneumocystis carinii require chronic use of medications to prevent recurrence.

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