What is the treatment approach for pneumonitis?

Treatment of Pneumonitis

For drug-induced pneumonitis, treatment is severity-based: grade 1 requires monitoring only, grade 2 requires drug discontinuation plus oral prednisone 1 mg/kg daily, and grade 3-4 requires hospitalization with high-dose IV methylprednisolone 2-4 mg/kg/day. 1, 2

Severity-Based Treatment Algorithm

Grade 1 (Asymptomatic, Radiologic Changes Only)

• Continue the causative therapy with close monitoring—corticosteroids are not required at this stage 1, 2
• Monitor symptoms and oxygen saturation every 2-3 days using pulse oximetry 1
• Obtain CT chest imaging to identify ground-glass opacities, patchy nodular infiltrates, or interstitial patterns 1
• Schedule weekly clinical visits for reassessment 2

Critical pitfall: Do not delay CT imaging for any new respiratory symptom—disease progression, infection, and pneumonitis must be formally excluded 2

Grade 2 (Symptomatic, Mild-Moderate)

• Immediately discontinue the suspected causative agent 1, 2
• Initiate oral corticosteroids: prednisone 1 mg/kg daily or equivalent 1, 2
• Taper steroids over 4-6 weeks minimum after clinical recovery 1
• Perform bronchoscopy with bronchoalveolar lavage (BAL) to exclude infections 1

Critical pitfall: Steroid tapering must be very slow (6+ weeks minimum) as relapses during tapering are well-documented; some patients require even longer tapers 1, 2

Grade 3-4 (Severe, Life-Threatening)

• Hospitalize immediately and permanently discontinue the offending agent 1, 2
• Administer high-dose IV corticosteroids: methylprednisolone 2-4 mg/kg/day or equivalent 1, 2
• Consider additional immunosuppressive agents (infliximab, mycophenolate mofetil, or cyclophosphamide) if no improvement after 48 hours 1
• For immune checkpoint inhibitor pneumonitis, administer broad-spectrum antibiotics in parallel if infectious status cannot be reliably assessed 1
• Perform bronchoscopy with BAL to exclude infections, particularly in this severity grade 1

Diagnostic Confirmation

• Improvement following drug cessation without glucocorticoid therapy strongly supports drug-related pneumonitis 1, 2
• Clinical improvement with glucocorticoid therapy supports but does not definitively confirm the diagnosis 1, 2
• Transbronchial or surgical lung biopsy may be considered when etiology is unclear, though not routinely required 1

Special Populations and Considerations

Immune Checkpoint Inhibitor (ICI) Pneumonitis

• Anti-PD-1/PD-L1 monoclonal antibodies cause pneumonitis in 2-4% of patients, with grade 3-4 events in 1-2% and fatal pneumonitis in 0.2% 2
• Combination immunotherapy (anti-PD-1/PD-L1 plus anti-CTLA4) increases pneumonitis risk 3-fold, with incidence reaching 10% versus 3% for monotherapy 2
• Patients with non-small cell lung cancer have more treatment-related deaths from pneumonitis compared to other tumor types 2
• Approximately 2% of non-small cell lung cancer or melanoma patients develop chronic pneumonitis persisting despite ICI discontinuation 2

Monitoring and Follow-Up

• Reassess clinical response on Days 2 and 3: check temperature, WBC, chest X-ray, oxygenation, purulent sputum, hemodynamic changes, and organ function 3
• If no improvement, search for other pathogens, complications, or alternative diagnoses 3
• Fatal cases have been reported, making vigilant monitoring of all respiratory symptoms mandatory 2