A case of isoniazid sodium methanesulfonate induced interstitial pneumonia

A 71-year-old male was admitted to our hospital with dyspnea on effort. He had been prescribed rifampicin, isoniazid sodium methanesulfonate (IHMS), and ethambutol for pulmonary tuberculosis, and ursodesoxycholic acid for alcoholic liver dysfunction. The chest HRCT revealed diffuse ground-glass attenuation with interlobular interstitial thickening. BALF showed lymphocytosis, and TBLB revealed organizing pneumonia. All medications were interrupted, and his respiratory failure and chest HRCT findings were improved. He started again medications excluding IHMS, his condition continued to improve further. DLST to causative IHMS was negative with peripheral blood lymphocytes, but was positive with lymphocytes from BALF. Therefore, we diagnosed this case as having IHMS induced interstitial pneumonia. In the past, 5 cases of isoniazid induced interstitial pneumonia were reported, but IHMS induced interstitial pneumonia has not been reported. Clinicians need to be aware of drug induced interstitial pneumonia by anti-tuberculosis drugs including IHMS in patients receiving anti-tuberculosis drugs.