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Pneumocystis jiroveci

Up CAP Fungal pneumonia Guidelines HAP Mycoplasma Pneumocystis jiroveci


Updated November 2006 by Charles Gomersall

Epidemiology

  • previously referred to as Pneumocystis carinii. This term, however, now refers only to pneumocystis that infects rodents. Pneumocystis jiroveci refers to the distinct species that infects humans. The abbreviation PCP is still used to refer to pneumocystis pneumonia.
  • incidence amongst patients with AIDS has fallen substantially with the widespread use of prophylaxis and effective anti-retroviral therapy. Incidence among these patients in Western Europe and USA is 2-3 cases per 100 person-years
  • majority of cases in AIDS patients occur among patients who are not receiving HIV care or among patients with advanced immunosuppression (CD4+ T lymphocytes <100 cells/µl)
  • disease probably occurs by new acquisition and reactivation. Two thirds of healthy children have evidence of previous infection with Pneumocystis jiroveci by 2-4 years.

Clinical features

  • Insidious onset
  • Dry cough
  • Breathlessness and tachypnoea
  • Sputum production rare
  • Background of fatigue,and weight loss
  • Fever common
  • Crackles in the chest rare
  • Cyanosis is severe cases
  • Course more likely to be fulminant in non-HIV patients
  • Approximately 15% of patients have another concurrent cause for respiratory failure (eg Kaposi sarcoma, TB, bacterial pneumonia)`

Investigations

  • raised LDH common but non specific

CXR

  • diffuse bilateral perihilar interstitial shadowing. In early stages this is very subtle and easily missed
  • normal in 10%
  • atypical in further 10%:
    • nodules
    • asymmetric disease
    • blebs and cysts
    • localized to upper lobes
    • pneumothorax
  • none of the changes are specific for PCP and may be seen in other lung diseases associated with AIDS
  • pleural effusions, hilar or mediastinal lymphadenopathy unusual in PCP but common in mycobacterial infection or Kaposi's or lymphoma

Demonstration of organisms

Spontaneously expectorated sputum has low sensitivity and should not be submitted to the laboratory to diagnose PCP

Treatment can be initiated before making a definitive diagnosis as organisms persist in clinical specimens for days-weeks are starting treatment

Induced sputum

  • patient inhales nebulised hypertonic saline from and ultrasonic nebuliser. This provokes bronchorrhoea and the patient coughs up material containing cysts and trophozoites
  • time consuming and requires meticulous technique
  • sensitivity <50% to >90%

Bronchoalveolar lavage

  • specimens should be sent for cytology; leads to diagnosis in over 90% of cases

Histology

  • sensitivity of both transbronchial biopsy and open lung biopsy ≥95%
  • not usually necessary

Treatment

Severe cases

NB treat as soon as diagnosis thought to be a possibility

Although there is some suggestion of potential benefit for early antiretroviral therapy for patients with HIV and PCP some centres delay initiation of antiretrovirals until after completion of anti-PCP treatment. Treatment with antiretrovirals may be associated with an immune reconstitution syndrome which may make management difficult.

1st line treatment

  • trimethoprim plus sulphamethoxazole (co-trimoxazole)
    • 15-20 mg/kg/day + 75-100 mg/kg/day for 3 weeks
    • common side effects in HIV patients include fever, nausea, vomiting, skin rash, myelotoxicity, hepatitis
    • if WBC count falls reduce dose by 25%

Alternatives

  • pentamidine
    • 4 mg/kg/day IV for 3 weeks
    • more severe side effects than co-trimoxazole (hypoglycaemia, hyperglycaemia, pancreatitis, nephrotoxicity, hepatotoxicity)
  • primaquine with clindamycin
    • adverse effects: anaemia, rash, fever, diarrhoea, methaemoglobinaemia
  • trimetrexate (± oral dapsone) with leucovorin for 3 weeks
    • less effective than trimethoprim plus sulphamethoxazole but can be used if trimethoprime-sulphamethoxazole is not tolerated
    • leucovorin should be continued for 3 days after the last trimetrexate dose
    • adverse effects of trimetrexate: bone marrow suppression, fever, rash, hepatitis
    • adverse effects of dapsone: methaemoglobinaemia, haemolysis, rash, fever

PLUS

  • Glucocorticoids
    • begin as early as possible (and at least within 3 days) after the onset of anti-pneumocystis therapy in patients with PaO2< 70 mmHg or A-a gradient > 35 mmHg
    • prednisolone 40 mg orally twice daily for 5 days followed by 20 mg twice daily for 5 days and then 20 mg per day until the end of anti-pneumocystis treatment
      • methylprednisolone at 75% of respective prednisolone dose if parenteral administration necessary

Response to treatment

  • in those that deteriorate or fail to improve (NB response time 4-8 days):
    • consider possibility of co-pathogens and consider (re-) bronchoscopy
    • deterioration in first few days usual in those patients who are not given steroids
    • consider second line therapy
    • consider giving diuretics (patients often fluid overloaded)

Prognosis

  • up to 40% of patients with HIV related PCP who require mechanical ventilation survive to hospital discharge

Further reading

Treating Opportunistic Infections among HIV-Infected Adults and Adolescents: Recommendations from CDC, the National Institutes of Health, and the HIV Medicine Association/Infectious Diseases Society of America


©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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