Methotrexate-associated pneumonitis: usefulness of lung ultrasound

José S Cortés1, Javier Correa1, Wilder Carvajal1

  • 1Universidad Nacional de Colombia.

ARP Rheumatology
|January 2, 2026
PubMed
Abstract

Insights

Methotrexate-associated pneumonitis (MTX-Pneu) is a rare hypersensitivity reaction. Prompt recognition and treatment with methotrexate discontinuation and corticosteroids lead to favorable outcomes.

Area of Science:

  • Rheumatology
  • Pulmonology
  • Radiology

Background:

  • Methotrexate-associated pneumonitis (MTX-Pneu) is an uncommon, idiosyncratic hypersensitivity reaction.
  • It can occur in patients treated with methotrexate for rheumatoid arthritis and may present acutely.

Purpose of the Study:

  • To report a case of MTX-Pneu in a patient with rheumatoid arthritis.
  • To highlight the diagnostic and monitoring utility of lung ultrasound.

Main Methods:

  • A 75-year-old woman with rheumatoid arthritis developed acute respiratory symptoms after starting methotrexate.
  • Diagnostic workup included lung ultrasound and chest CT.
  • Treatment involved methotrexate discontinuation and increased corticosteroid dosage.

Main Results:

  • The patient presented with fever, cough, and dyspnea, with bilateral pulmonary involvement on imaging.
  • Following treatment, clinical symptoms and imaging findings fully resolved.
  • Lung ultrasound and CT confirmed MTX-Pneu.

Conclusions:

  • MTX-Pneu is an idiosyncratic reaction, distinct from rheumatoid arthritis-associated interstitial lung disease.
  • Early methotrexate withdrawal and corticosteroid therapy are crucial for favorable prognosis.
  • Lung ultrasound may serve as a rapid bedside tool for MTX-Pneu detection and monitoring.