Propylthiouracil-induced anti-neutrophil cytoplasmic antibody-associated vasculitis mimicking Kawasaki disease

Propylthiouracil-Induced Skin Vasculitis

The use of propylthiouracil (PTU) is associated with the development of autoantibodies, namely, antineutrophil cytoplasmic antibodies (ANCAs), which are associated with the pathogenesis of ANCA-associated systemic vasculitis, most often related to the myeloperoxidase subtype (ANCA-MPO). The authors report the case of a 61-year-old woman on PTU for one year who was referred to Internal Medicine for a three-month evolution of painless non-blanching purple patches, non-pruriginous, involving the chest and legs. The autoimmunity revealed ANCA antibody positivity, with a cutaneous biopsy compatible with leukocytoclastic vasculitis/necrotizing vasculitis with involvement of small and medium-sized vessels. Clinical improvement was noted after the drug was discontinued, with the resolution of the analytical changes.

[Purpura in a young woman with hyperthyroidism]

INTRODUCTION

Propylthiouracil (PTU) is a synthetic antithyroid drug that can induce ANCA-associated vasculitis.

OBSERVATION

A 27-year-old woman diagnosed with Graves' disease was on PTU for the past 10 years. She developed purpuric lesions of the legs and on the tip of the nose diagnosed as vasculitis. ANCAs were positive, with anti-MPO and anti-PR3 on blood ELISA. After discontinuation of PTU, she was able to fully recover.

CONCLUSION

All synthetic antithyroid drugs can induce ANCA-associated vasculitis, more often PTU. In most cases, antibodies are directed against MPO. Dual anti-MPO and anti-PR3 positivity is possible, but rare. The mechanism could be through an accumulation of PTU in neutrophils, altering the structure of MPO and making it immunogenic. PTU can also induce ANCA-free or lupus vasculitis, maculopapular rashes or urticaria. Many other drugs can induce ANCA-associated vasculitis.