Toxoplasma pneumonia.

Toxoplasma gondii, an obligate intracellular parasite, is the causal agent of significant morbidity and mortality worldwide. In the presence of a normal immune response, the pathogen becomes latent and the immunocompetent host remains chronically infected throughout life, often without clinical disease. In the case of the patient with the acquired immunodeficiency syndrome (AIDS) or other defects in cell-mediated immunity, the infection reactivates and is most often manifest as toxoplasmic encephalitis. Toxoplasmic pneumonitis follows the same pathogenetic mechanism, but occurs less frequently than either toxoplasmic encephalitis or other opportunistic pneumonias, such as a Pneumocystis carinii pneumonia (PCP). During the past decade the incidence of toxoplasma pneumonia has increased in immunocompromised patients and as a result, it has become essential that clinicians include this infectious agent in the diagnostic testing and differential diagnostic of pneumonia in T gondii seropositive patients. Most patients present with clinical and radiographic findings suggestive of PCP. The onset of disease tends to be more rapid, however. Diagnosis is based upon a high degree of clinical suspicion and demonstration of T gondii in bronchioalveolar lavage fluid and/or lung biopsy specimens. Effective therapy, pyrimethamine and sulfadiazine or trisulfapyrimidine with folinic acid, is available if initiated promptly.