HIV: <i>Pneumocystis jiroveci</i> pneumonia

Whilst the organism Pneumocystis carinii is now referred to as Pneumocystis jiroveci, the term Pneumocystis carinii pneumonia (PCP) is still in common use

• Pneumocystis jiroveci is an unicellular eukaryote, generally classified as a fungus but some authorities consider it a protozoa
• PCP is the most common opportunistic infection in AIDS
• all patients with a CD4 count < 200/mm³ should receive PCP prophylaxis

Features

• dyspnoea
• dry cough
• fever
• very few chest signs

Pneumothorax is a common complication of PCP.

Extrapulmonary manifestations are rare (1-2% of cases), may cause

• hepatosplenomegaly
• lymphadenopathy
• choroid lesions

Investigation

• CXR: typically shows bilateral interstitial pulmonary infiltrates but can present with other x-ray findings e.g. lobar consolidation. May be normal
• exercise-induced desaturation
• sputum often fails to show PCP, bronchoalveolar lavage (BAL) often needed to demonstrate PCP (silver stain shows characteristic cysts)

Management

• co-trimoxazole
• IV pentamidine in severe cases
• steroids if hypoxic (if pO2 < 9.3kPa then steroids reduce risk of respiratory failure by 50% and death by a third)

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