Synopsis
Recognise Pneumocystis pneumonia across HIV and non-HIV immunosuppression, combine oxygen assessment with organism detection, start weight-based co-trimoxazole promptly, add corticosteroids only for supported hypoxaemic indications, and prevent recurrence.
- Pneumocystis jirovecii pneumonia is an opportunistic fungal pneumonia associated with advanced HIV, prolonged corticosteroids, haematological malignancy, transplantation and selected immune-modulating therapies.
- HIV-associated disease often evolves over weeks with dry cough, fever and exertional breathlessness; non-HIV disease may progress rapidly with more severe hypoxaemia and fewer organisms.
- First-line imaging is chest radiography followed by CT when suspicion persists; bilateral diffuse ground-glass opacity is typical but not specific.
- Preferred microbiological confirmation is Pneumocystis PCR or microscopy from induced sputum or bronchoalveolar lavage; a highly sensitive PCR must be interpreted against fungal burden and clinical probability because colonisation occurs.
- Serum 1,3-beta-D-glucan is a useful supportive test and a low result can reduce probability, but it is not species specific and cannot establish PJP alone.
- First-line treatment is co-trimoxazole delivering trimethoprim 15 to 20 mg/kg/day plus sulfamethoxazole 75 to 100 mg/kg/day in three or four divided doses.
- Treat HIV-associated PJP for 21 days; non-HIV duration is commonly 14 to 21 days and should be individualised with infection specialists.
- Use adjunctive prednisolone for moderate-to-severe HIV-associated disease: 40 mg twice daily on days 1 to 5, 40 mg once daily on days 6 to 10, then 20 mg once daily on days 11 to 21.
Key red flags
Resting hypoxaemia, rapid oxygen escalation, marked exertional desaturation, severe tachypnoea or respiratory fatigue requires urgent critical-care assessment.
Room-air arterial oxygen below 9.3 kPa or an alveolar-arterial gradient above 4.7 kPa in HIV-associated PJP supports early adjunctive corticosteroid treatment.
A pneumothorax, pneumomediastinum or cystic lung lesions can cause sudden pleuritic pain and decompensation and require immediate imaging and respiratory care.
A normal early chest radiograph does not exclude PJP; persistent compatible symptoms in a high-risk host require CT and organism-directed sampling.
Failure to improve after four to eight days raises wrong diagnosis, co-infection, drug toxicity, poor absorption, immune reconstitution or a complication rather than automatic resistance.
New PJP should prompt urgent HIV testing with consent and review of corticosteroid, transplant, chemotherapy or immune-modulator exposure.
Progressive exertional dyspnoea, dry cough, fever, fatigue and weight loss develop over days to weeks, with initially subtle examination findings.
Fever, severe hypoxaemia and diffuse pneumonitis may evolve over only a few days during corticosteroid, transplant or haematology treatment.
Investigation priorities
Grade severity and determine need for corticosteroid and critical-care escalation.
Identify diffuse pneumonitis and complications while evaluating alternative diagnoses.
Management branches
An immunocompromised patient develops progressive dry cough, fever, dyspnoea or unexplained oxygen impairment.
- Use ABCDE, measure resting and exertional oxygen saturation, obtain a room-air arterial blood gas where safe, and involve critical care for escalating oxygen or fatigue.
- Obtain chest radiography and urgent thin-section CT when the film is normal or non-diagnostic but clinical suspicion remains high.
- Send induced sputum or BAL for Pneumocystis PCR and microscopy plus bacterial, mycobacterial, viral and fungal studies appropriate to the host.
- Start treatment after sampling when possible, but do not delay for bronchoscopy in a patient whose respiratory physiology is deteriorating.
PJP is confirmed or strongly suspected and treatment cannot safely await final molecular results.
- Calculate dosing from the trimethoprim component: 15 to 20 mg/kg/day trimethoprim with 75 to 100 mg/kg/day sulfamethoxazole, divided every six to eight hours.
- Use intravenous treatment for severe hypoxaemia, vomiting or unreliable absorption; switch to oral treatment once stable and absorbing without reducing the total daily dose inadvertently.