Pneumocystis jirovecii pneumonia is characterised by progressive dyspnoea with dry cough and fever.Chest X ray shows bilateral interstitial infiltrate spreading out from hilar regions.High resolution CT scan is more sensitive,showing 'ground-glass' interstitial infiltrates.Diagnosis is made with silver stains,PCR,immunofluorescence of bronchoalveolar lavage(BAL)/induced sputum.Treatment is with high dose co-trimoxazole;together with adjunctive steroids if the patient is hypoxic. Reference: Davidson edition23rd pg 584