Antineutrophil cytoplasmic antibody-positive vasculitis in a patient with graves disease: cross-reaction between propylthiouracil and methimazole.
OBJECTIVE
To alert clinicians about the risk of vasculitis and cross-reactivity of antithyroid medication.


METHODS
We describe the clinical course and medical management of the study patient.


RESULTS
A 25-year-old woman with hyperthyroidism developed antineutrophil cytoplasmic antibody-positive vasculitis after 15 months of propylthiouracil therapy. Her condition improved when propylthiouracil was withdrawn, but recurred when she was prescribed methimazole. Propylthiouracil and methimazole are commonly used antithyroid medications, and propylthiouracil is a well-recognized cause of drug-induced vasculitis. Cross-reactivity between the 2 drugs is likely, but it has not been reported previously with regard to vasculitis. Many patients with propylthiouracil-induced vasculitis have been switched to methimazole.


CONCLUSIONS
Awareness of this rare, but potentially serious, adverse drug reaction is important because prompt discontinuation of medication is essential. Cross-reactivity between propylthiouracil and methimazole must be considered when selecting alternative therapies.
Ahmed
Khulood
K
Department of Internal Medicine, Texas Tech University Health Sciences Center, Odessa, Texas, USA.
Rao
Sneha
S
Simha
Vinaya
V
D000328:Adult; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000378:metabolism*; D013956:Antithyroid Agents / Q000009:adverse effects* / Q000627:therapeutic use; D004347:Drug Interactions; D005260:Female; D006111:Graves Disease / Q000150:complications* / Q000378:metabolism; D006801:Humans; D008713:Methimazole / Q000009:adverse effects* / Q000627:therapeutic use; D011441:Propylthiouracil / Q000009:adverse effects* / Q000627:therapeutic use; D014657:Vasculitis / Q000188:drug therapy* / Q000378:metabolism*
D019268:Antibodies, Antineutrophil Cytoplasmic; D013956:Antithyroid Agents; D008713:Methimazole; D011441:Propylthiouracil