Metformin-Induced Eosinophilic Interstitial Lung Disease

Area of Science:

• Pulmonology
• Pharmacology
• Internal Medicine

Background:

• Metformin is a first-line oral hypoglycemic agent for type 2 diabetes mellitus.
• While generally safe, metformin can cause various side effects, and its pulmonary effects are debated.
• Previous reports have linked metformin combinations to interstitial lung disease, but monotherapy's role is less understood.

Observation:

• A 64-year-old male presented with progressive dyspnea.
• The patient was on metformin monotherapy for type 2 diabetes.
• Diagnostic workup including pulmonary function tests, HRCT, and bronchoscopy confirmed eosinophilic interstitial lung disease (ILD).

Findings:

• Metformin was identified as the sole causative agent for eosinophilic pneumonitis in this patient.
• Other potential causes of eosinophilic pneumonia were systematically excluded.
• Discontinuation of metformin led to significant clinical improvement in the patient's respiratory condition.

Implications:

• This case represents the first documented instance of metformin monotherapy inducing eosinophilic pneumonitis.
• It underscores the importance of considering drug-induced lung injury, even with commonly prescribed medications.
• Clinicians should maintain a high index of suspicion for metformin-induced ILD in diabetic patients presenting with unexplained respiratory symptoms.