Pneumocystis Carinii Pneumonia
Because of its association with human immunodeficiency virus (HIV) infection, Pneumocystis carinii pneumonia (PCP), an opportunistic infection, has increased in incidence since the 1980s. It occurs in the following hosts: premature or malnourished infants; children with primary immunodeficiency disease; patients receiving immunosupressive therapy (particularly glucocorticoids) for cancer, organ transplantation, or other disorders; or people with acquired immunodeficiency syndrome (AIDS). The organism remains a leading cause of opportunistic infection and death among patients with AIDS in industrialized countries.
Causes
P. carinii, the cause of PCP, is usually classified as a protozoan, although some investigators consider it more closely related to fungi. The organism exists as a saprophyte in the lungs of humans and various animals. Part of the normal flora in most healthy people, P. carinii becomes an aggressive pathogen in the immunocompromised patient. Impaired cellmediated (T-cell) immunity is thought to be more important than impaired humoral (B-cell) immunity in predisposing the patient to PCP, but the immune defects involved are poorly understood.
The primary transmission route seems to be air, although the organism is already resident in most people. The incubation period probably lasts for 4 to 8 weeks. Impaired cellular immunity is the major factor that predisposes a person to pneumocytosis. Defects in B-cell function also play a role.
The organism invades the lungs bilaterally and multiplies extracellularly. As the infestation grows, alveoli fill with organisms and exudate, impairing gas exchange. The alveoli hypertrophy and thicken progressively, eventually leading to extensive consolidation.
Complications
PCP can progress to pulmonic insufficiency and possibly death if left untreated. Disseminated infection occurs in both AIDS and non-AIDS patients.
Assessment
The patient typically has a history of an immunocompromising condition or procedure, such as HIV infection, leukemia, lymphoma, or organ transplantation.
PCP begins insidiously with increasing shortness of breath and a nonproductive cough. Anorexia, generalized fatigue, and weight loss may be reported. Although the patient may have hypoxemia and hypercapnea, he may not exhibit significant clinical symptoms. Throughout the illness, he may report a low-grade, intermittent fever.
Inspection may reveal tachypnea, dyspnea, and accessory muscle use when the
patient breathes. With acute illness, he may appear cyanotic.
patient breathes. With acute illness, he may appear cyanotic.
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