Approach to Fever and Pulmonary Infiltrates in Immunocompromised Hosts (e.g. post-BMT patients)

General principles:

• Minor abnormalities on CXR must be investigated, preferably with CT
• Multiple simulataneous pulmonary processes are common
• As the differential is quite large, invasive studies such as bronschopy and biopsies are often necessary
• Serologies are generally not useful in the acute phase, due to inability to generate Abs

Etiologies – basically the key distinction is Infectious vs Noninfectious.

 

I.  Infectious
1) Bacterial – all the usual players for both CAP and HCAP, and remember that aspiration pneumonia is particularly common
2) Fungal - #1 = Aspergillus, also other molds, and Cryptococcus, Histo, Cocci
3) Viruses – Respiratory viruses – Influenza, Parainfluenza, RSV, Adenovirus, also CMV and HHV-6 are common
4) PCP – risk depends on whether or not the pt was on prophylaxis (and compliant)
5) Nocardia
6) Mycobacterial, including TB
7) Other

 

 

II.  Noninfectious
1) Drug-induced Lung injury – Many chemotherapy drugs and immunosuppressants have pulmonary toxicities
Examples:

• Methotrexate, Bleomycin, Procarbazine à fever, cough, infiltrates, eosinophilia
• Cyclophosphamide – Interstitial lung disease and pulmonary fibrosis
• Sirolimus – interstitial pneumonitis
• BCNU – interstitial lung disease

 

2) Radiation-induced Lung Injury – can present acutely, or after several months with bilateral infiltrates/interstitial lung disease

 

3) Diffuse Alveolar Hemorrhage – presents with cough, fever, respiratory distress, sometimes with gross hemoptysis (~15-33% of the time).  Unclear pathophysiology.  On BAL, get progressively bloodier aliquos of lavage fluid.  Radiographically, has bilateral patchy infiltrates and ground glass opacities.  Occurs with allo BMT more frequently than auto.  Treatment is high dose steroids although the data for this is limited, as well as correcting coagulopathies and thrombocytopenia. 

 

4) Transfusion-related Acute Lung Injury (TRALI) – BMT and Heme/Onc patients are clearly at risk for this given their transfusion requirements

 

5) Pulmonary edema – cardiogenic (either due to preexisting CHF or chemo-induced cardiomyopathy, + large amounts of fluids that are often given post-transplant) or noncardiogenic (i.e., ARDS due to sepsis)

 

6) Pulmonary Alveolar Proteinosis – fairly uncommon, dx’d by BAL – see milky appearance of fuild with positive stain for lipoproteins

• Basic approach involves taking a good history and physical, focusing on meds especially chemotherapy, radiation exposure, immunosuppressive regimen, travel history, sick contacts, other exposures, etc.
• CT chest is quite helpful, as certain patterns can help point you in one direction (although none are specific): Consolidations - usually bacterial PNA; Ground Glass Opacities - Edema vs PCP vs viral vs atypicals vs DAH vs Drug rx; Nodular - fungal; Cavitation - MBT, fungal, nocardia, Klebsiella.
• Invasive tests such as BAL and even VATs are sometimes necessary since the ddx is so broad.
• Empiric broad spectrum antibiotics +/- antifungals and antivirals are generally indicated.

 

(Chanu Rhee MD, 1/25/11)