Metformin-Induced Eosinophilic Interstitial Lung Disease

Metformin, a mainstay treatment for type two diabetes mellitus has several side effects, ranging from mild to life-threatening ones. One report has found the combination of metformin/glibenclamide a culprit for interstitial lung disease. Other studies have shown that metformin has a protective effect on the lungs. We report a rare case of a 64-year-old male who presented with progressive dyspnea while he was on metformin alone. He was diagnosed with eosinophilic interstitial lung disease (ILD). This was confirmed by a pulmonary function test (PFT), high-resolution chest computed tomography scan (HRCT), and bronchoscopy with bronchoalveolar lavage (BAL). Known causes for eosinophilic pneumonia were excluded, and the patient's condition improved significantly after withdrawing metformin. We report this case due to the rarity of the condition. In fact, this is the only case in the literature, of metformin as the sole agent causing eosinophilic pneumonitis.