Pneumocystis carinii is an important, but sporadic, opportunistic pulmonary
pathogen in immunosuppressed HIV seronegative persons. Historically, patie
nts at highest risk for P carinii pneumonia are included infants with sever
e malnutrition, children with primary immunodeficiencies, patients with hem
atological malignancies, and recipients of solid organ or bone marrow trans
plants. Recently, solid tumor patients, in particular those receiving high-
dose corticosteroids for brain neoplasms, and patients with inflammatory or
collagen-vascular disorders, especially patients with Wegener granulomatos
is receiving immunosuppressive therapy, have been identified as subgroups a
t increased risk for P carinii pneumonia. Other factors associated with P c
arinii pneumonia include the intensity of the immunosuppressive regimen and
tapering doses of corticosteroids. Because P carinii pneumonia is associat
ed with significant morbidity and mortality, it is important to identify hi
gh-risk patient populations to administer effective chemoprophylactic agent
s, such as trimethoprimsulfamethoxazole.