Hundreds of thousands of cases of Pneumocystis lung infections are seen each year, primarily in immunosuppressed patients.
Pneumocystis pneumonia, PCP, PJP, Pneumocystis pneumonitis
– In HIV/AIDS patients, PCP is a subacute disease with fever, cough, weight loss, diarrhoea and increasing breathlessness. Prodromal features are often present for two to three weeks before the breathlessness becomes clinically problematic.
– In other immunodeficient patients, PCP is a more rapidly progressive disease with more prominent radiological findings and wheeze.
Pneumocystis jirovecii (formerly carinii)
Worldwide distribution. ~2.8 million with advanced HIV/AIDS infection are at risk. Conservative estimates suggest ~400,000 cases annually, but this is likely to be an underestimate of the true burden. PCP rates rise with GDP and decreasing numbers of TB cases, but the reasons for this are unclear.
HIV/AIDS patients with CD4 cells <250 x 106/L (and especially <200 x 106/L).
Transplant recipients, corticosteroid-treated patients (e.g. those with brain tumours on dexamethasone), malnourished children. Patients with hypogammaglobulinaemia, or acute/chronic leukaemia, or lymphoma.
– SPECIMEN: usually induced sputum and BAL fluids. Spontaneously-produced sputum and oral mouth-wash samples can also be used.
– DETECTION: best with real-time PCR or immunofluorescence. Beta-D-glucan is usually raised in blood and can assist with diagnosis. Culture is not possible because the microorganism does not grow in any known culture media. There is a new PCR assay being tested for efficacy against PCP.
Lung or other tissue biopsy and subsequent histology are sometimes necessary for diagnosis.
– First-line: cotrimoxazole/trimethoprim with corticosteroids for moderate or severe disease.
– Second-line: pentamidine or combination of clindamycin/primaquine. Mild cases can be treated with trimethoprim and dapsone or atavaquone.
If diagnosed promptly, the survival is 80-90% in HIV/AIDS in the western world. In non-AIDS patients, the survival is only 50%. Prevention of subsequent episodes is critical with prophylaxis, while immunocompromised. Patients with PCP should be isolated, as it is transmissible to other immunocompromised patients.