What is the treatment approach for pneumonitis?

Treatment of Pneumonitis

For drug-induced pneumonitis, treatment is severity-based: grade 1 requires monitoring only while continuing therapy; grade 2 requires stopping the offending agent and starting oral prednisone 1 mg/kg daily; grade 3-4 requires hospitalization, permanent drug discontinuation, and high-dose IV methylprednisolone 2-4 mg/kg/day, with additional immunosuppression if no improvement within 48 hours. 1

Severity-Based Treatment Algorithm

Grade 1 Pneumonitis (Asymptomatic Radiologic Changes)

• Continue the causative therapy with close monitoring—no corticosteroids are needed at this stage 1, 2
• Perform CT chest imaging to identify characteristic ground-glass opacities or patchy nodular infiltrates 1
• Monitor symptoms and oxygen saturation every 2-3 days using pulse oximetry 2
• Schedule weekly clinical visits for ongoing assessment 2
• Escalate treatment immediately if respiratory symptoms develop (cough, dyspnea, chest pain), oxygen saturation decreases, or radiographic progression occurs 2

Grade 2 Pneumonitis (Symptomatic but Mild-Moderate)

• Discontinue the suspected causative agent immediately 1
• Initiate oral prednisone 1 mg/kg daily (or equivalent corticosteroid) 1
• Consider bronchoscopy with bronchoalveolar lavage to exclude infectious etiologies 1
• Taper steroids over 4-6 weeks after clinical recovery 1
• Monitor closely for relapse during tapering, as recurrence has been reported 1

Grade 3-4 Pneumonitis (Severe or Life-Threatening)

• Hospitalize the patient immediately 1
• Permanently discontinue the offending agent—do not rechallenge 1
• Administer high-dose IV methylprednisolone 2-4 mg/kg/day (or equivalent) 1
• For immune checkpoint inhibitor pneumonitis, add broad-spectrum antibiotics empirically if infectious status cannot be reliably assessed 1
• If no improvement after 48 hours of high-dose steroids, add additional immunosuppressive agents: infliximab, mycophenolate mofetil, or cyclophosphamide 1
• Use a very slow steroid taper over 6+ weeks for immune checkpoint inhibitor-related cases, as relapses are common with rapid tapering 1

Diagnostic Confirmation

• CT chest is the preferred imaging modality to identify pneumonitis patterns 1
• Bronchoscopy with BAL should be performed for grade 2 or higher to exclude infections, particularly in immunocompromised patients 1
• Transbronchial or surgical lung biopsy may be considered when etiology remains unclear, though not routinely required 1
• Clinical improvement after drug cessation without glucocorticoids strongly supports drug-induced pneumonitis, while improvement with glucocorticoids is supportive but not definitive 1

Special Populations and Considerations

Immune Checkpoint Inhibitor Pneumonitis

• Incidence varies from 0-10% overall (2.7% general incidence), with higher rates in combination therapy (10%) versus monotherapy (3%) 2
• Patients with non-small cell lung cancer and renal cell carcinoma have higher risk than melanoma patients 2
• Approximately 2% develop chronic pneumonitis persisting despite drug discontinuation 2
• Requires particularly slow steroid tapering (6+ weeks minimum) due to high relapse rates 1

Bleomycin-Induced Pneumonitis

• Can occur at doses as low as 136 units (well below the traditional 200-unit threshold) 3
• Presents with dyspnea and dry cough; radiographic patterns may be asymmetric or unilateral 3
• Requires prolonged corticosteroid therapy over many months to maintain improvement 3
• Tapering steroids prematurely leads to symptom and radiographic recurrence 3
• Mortality can be 60% if untreated or inadequately treated 3

Hypersensitivity Pneumonitis (Fibrotic)

• Antigen avoidance is the most critical intervention and the only truly effective treatment when identified early 4, 5
• For fibrotic hypersensitivity pneumonitis with progression despite immunosuppression, antifibrotic medications can be used as second-line therapy 5
• Corticosteroids remain first-line pharmacotherapy, though other immunosuppressive agents are increasingly used by experts 5
• Prolonged corticosteroid therapy is often required, similar to drug-induced cases 3

Critical Pitfalls to Avoid

• Do not use pulmonary function tests to monitor treatment response—they remain abnormal despite clinical and radiographic improvement 3
• Never taper steroids rapidly in immune checkpoint inhibitor pneumonitis—this leads to high relapse rates requiring reinitiation of therapy 1
• Do not rechallenge with the offending agent in grade 3-4 pneumonitis—permanent discontinuation is mandatory 1
• Always exclude infection before attributing symptoms solely to pneumonitis, especially in grade 2 or higher severity 1
• Be aware that allergic symptoms may recur after initial successful treatment when symptomatic therapy is discontinued, requiring prolonged observation 6