Pneumonia in the Immunocompromised

OVERVIEW

• the numbers of immunocompromised patients is increasing c/o improved solid-organ and haemopoietic transplants and the expanded use of immunomodulatory therapies.
• pulmonary infections = most frequent complication with high mortality

HISTORY

• < 30 days post transplant – bacteria, fungi, HSV, respiratory viruses
• 2-6 months post transplant – bacteria, fungi, CMV, EBV, Pneumocystis carinii, Listeria
• > 6 months post transplant – community viruses and bacteria, opportunistic infections

EXAMINATION

• signs may be not as fulminant due to obtunded immunological response

INVESTIGATIONS

CXR

Local Infiltrates

• gram –ve rods
• staph aureus
• aspergillus
• malignancy
• Cryptococcus
• nocardia
• mucomycosis
• pneumocystis carinii
• Tb
• legionella
• radiation pneumonitis

Diffuse Infiltrates

• CMV
• HSV
• PCP
• drug reaction
• non-specific pneumonitis
• advanced aspergillus
• malignancy
• TRALI

To see list of pathogens associated with the different types of immunodeficiency see “Infectious Diseases – Specific Infections and Causative Organisms”

Sputum

• low sensitivity
• indicated as upper respiratory tract organisms likely to be causing pneumonia

Bronchoscopy

• consider early in management once infiltrate appears
• provides diagnosis in 50-80% of cases
• BAL is very reliable technique

Open Lung Biopsy

• rare, but diagnostic yield high

CT Chest

• important in the diagnosis of invasive pulmonary aspergillosis: halo sign (haemorrhage pulmonary nodule), air-crescent sign (cavitation)
• if CXR looks normal -> get CT

MANAGEMENT

• Bacterial infection
  –> cefuroxime + erythromycin -> imipenem
• CMV
  –> focarnet, ganciclovir
• Pneumocysttis jiroveci (carinii) –
  > trimethoprim-sulphamethoxazole
  + corticosteroids should be used in those with HIV + hypoxia: prednisone 1mg/kg Q12hrly for 5 days
• Invasive Pulmonary Aspergillous
  — neutropenic = most susceptible
  — can perform surveillance with galacto-mannan (polysaccharide antigen of A. fumigatus)
  -> voriconazole or amphortericin B or itraconazole
  Candida
  — only truly pathogenic if fungaemia or lung tissue invasion demonstrated
  -> caspofungin (acts against Aspergillous too)
  Cryptococcus neoformans
  -> amphortericin B +/- flucytosine