Isoniazid associated, painful, bilateral gynaecomastia.

Gynaecomastia is a rarely reported adverse drug reaction due to isoniazid therapy. We describe a 25-year-old, human immunodeficiency virus (HIV)--negative man, who was started on antituberculosis treatment (ATT) with isoniazid (H), rifampicin (R), pyrazinamide (Z) and ethambutol (E) in the combination RHZE for the first two months and RH there on. After four months, while receiving RH, he developed painful bilateral gynaecomastia. ATT had to be stopped because of this adverse drug reaction. Gynaecomastia, however, persisted even after three months of cessation of therapy. A year later, the patient reported complete disappearance of pain and swelling, although right breast continued to appear larger than the left.