Synopsis
Identify Pneumocystis jirovecii pneumonia in HIV and non-HIV immune suppression, grade gas-exchange impairment, secure respiratory evidence without destabilising the patient, and deliver co-trimoxazole, selected corticosteroids and prevention safely. Confirm treatment against current BHIVA, BNF, eMC and local HIV, haematology or transplant protocols.
- Think of PJP with subacute dry cough, fever, exertional breathlessness, disproportionate hypoxaemia and bilateral ground-glass change in a person with impaired T-cell immunity.
- Risk includes untreated or advanced HIV, prolonged corticosteroids, haematological malignancy, transplantation and selected biologic or cytotoxic therapies; a normal total white count does not reassure.
- Chest radiography can be normal early. Thin-section CT usually shows diffuse or patchy bilateral ground glass but is not pathogen-specific.
- Measure arterial blood gases on room air when safe, or document inspired oxygen carefully, because PaO2 and the alveolar-arterial gradient determine severity and the HIV corticosteroid decision.
- Induced sputum or BAL PCR and microscopy provide microbiological support; PCR is very sensitive and may detect colonisation, so interpret organism burden with the syndrome.
- High-dose co-trimoxazole, calculated by the trimethoprim component, is first-line treatment; monitor potassium, renal function, blood count and rash closely.
- In HIV-associated moderate-to-severe PJP, start adjunctive corticosteroid early when PaO2 is below 9.3 kPa or the alveolar-arterial gradient is at least 4.7 kPa; non-HIV evidence is less certain.
- Evaluate the cause of immune suppression, offer HIV testing with consent when status is unknown, and plan ART or secondary prophylaxis with the appropriate specialist team.
Key red flags
A patient receiving corticosteroids, chemotherapy, transplant immunosuppression or a T-cell-active biologic develops rapidly increasing oxygen needs and bilateral ground glass over days.
Cyanosis, respiratory fatigue, PaO2 below 9.3 kPa or a markedly widened alveolar-arterial gradient indicates significant disease. Early critical-care involvement is appropriate if oxygen needs rise.
Pneumatoceles can complicate PJP and predispose to spontaneous pneumothorax. Sudden pleuritic pain, unilateral loss of breath sounds or acute desaturation requires immediate assessment.
Investigation priorities
Grade hypoxaemia and establish whether HIV-associated disease meets the corticosteroid threshold; record FiO2 and, where safe, obtain the reference sample breathing room air.
Management branches
Compatible immune risk, CT pattern and hypoxaemia, with results pending.
- Stabilise using controlled oxygen to an individual target, obtain ABG and early critical-care review if oxygen needs or work of breathing rise; assess immediately for pneumothorax.
- Send induced sputum or BAL only when safe and collect tests for competing infections, but start co-trimoxazole promptly when clinical probability is high.
- Calculate the regimen by trimethoprim weight, adjust for renal function and obesity according to the local protocol, and divide the daily dose as specified.
- Review physiology, microbiology and toxicity daily; failure to improve should trigger an alternative-diagnosis and treatment-exposure review, not automatic dose escalation.