Pneumocystis carinii pneumonia PCP

Although recently recognised as being more like a fungus, P. carinii is considered under protozoa here. Nowadays PCP most commonly occurs in those at risk who fail to take adequate prophylaxis or who are newly diagnosed with HIV infection in advanced disease where it is frequently the presenting illness.

Clinical suspicion is aroused early in patients who are under regular medical supervision, leading to earlier diagnosis. Later diagnosis is asssociated with more severe disease and poorer treatment outcome. Techniques of diagnosis include sputum induction with nebulised saline; this obviates the need for bronchoscopy but the diagnostic sensitivity is lower. The use of lavage alone at bronchoscopy avoids transbronchial biopsy with its complications of haemorrhage and pneumothorax. Exercise oximetry and alternative imaging techniques with radiolabelled compounds are also being used in diagnosis. Monoclonal antibodies to pneumocystis proteins and sensitive DNA probes have been developed but have yet to reach the bedside. In the absence of a confirmatory test, a presumptive diagnosis may be made based on the clinical presentation and chest x ray appearances in a patient severely immunosuppressed and at risk.

High-dose intravenous co-trimoxazole for two to three weeks remains a standard first-choice regimen for severe PCP, but once fevers and symptoms have settled and blood gas values have improved the drug can be given by mouth. Side-effects are common, typically after 7—10 days. If co-trimoxazole treatment is not tolerated, alternative treatment regimens include either intravenous pentamidine or a combination of clindamycin and primaquine. Pentamidine is as effective as co-trimoxazole but has side-effects that can be life threatening and should be given

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