An uncommon side effect of thiamazole treatment in Graves' disease

Thionamides (such as thiamazole/methimazole) are a common first line treatment for Graves' disease. Common side effects include rash, urticaria, and arthralgia. However, thionamide treatment has also been associated with a variety of auto-immune syndromes. Here, we describe a patient presenting with mild arthritis after starting thiamazole. Although severe presentation warrants acute withdrawal of the causative agent, our case suggests that milder forms can be successfully treated with anti-inflammatory drugs alone. Recognition of the syndrome is key to warrant timely and effective treatment.