A tale of two patients with hypersensitivity reactions to levothyroxine

Hypothyroidism is common in the general population, and levothyroxine (LT4) is the treatment of choice. LT4 is well tolerated in the majority of the patients, and allergic reactions are rare, with only a few reported cases of LT4 drug hypersensitivity reactions (DHR) 1-3; However, due to the synthetic nature of this drug, it is suggested that hypersensitivity can be induced under certain pathologic conditions, such as autoimmune disorders 4. We present two cases of DHR to thyroid replacement therapy (TRT) with subsequent management by drug provocation test (DPT) and induction of drug tolerance (IDT).