Don’t Mistake It for RA: A Case of Antithyroid Arthritis Syndrome After Methimazole Initiation

Authors

Michael K. Viggiano, Hackensack Meridian Health Palisades Medical Center Internal Medicine Department, 7600 River Rd, North Bergen, NJ 07047Follow
Auda Baker, Hackensack Meridian Health Palisades Medical Center Internal Medicine Department, 7600 River Rd, North Bergen, NJ 07047
Diana Palanker, Hackensack Meridian Health Palisades Medical Center Internal Medicine Department, 7600 River Rd, North Bergen, NJ 07047
Ayrton Bangolo, 1. Hackensack Meridian Health Palisades Medical Center Internal Medicine Department, 7600 River Rd, North Bergen, NJ 07047
Anna Belyayeva, Hackensack Meridian Health Palisades Medical Center Internal Medicine Department, 7600 River Rd, North Bergen, NJ 07047
Iyad Baker, Hackensack Meridian Health Palisades Medical Center Internal Medicine Department, 7600 River Rd, North Bergen, NJ 07047

Abstract

Antithyroid arthritis syndrome (AAS) is a rare reaction to thionamides (e.g., methimazole) that can cause sudden, severe joint pain. It often gets mistaken for rheumatoid arthritis or lupus but typically improves within four weeks when the medication is stopped. A 51-year-old man with Graves’ disease developed a rash and disabling joint pain in multiple areas within weeks of starting methimazole. Labs showed elevated liver enzymes and CRP, but no autoimmune markers. Symptoms improved quickly after a short steroid taper and stopping the drug. This case shows how AAS can mimic autoimmune disease and why it is important to recognize early to avoid unnecessary treatment.

Recommended Citation

Viggiano, Michael K.; Baker, Auda; Palanker, Diana; Bangolo, Ayrton; Belyayeva, Anna; and Baker, Iyad (2026) "Don’t Mistake It for RA: A Case of Antithyroid Arthritis Syndrome After Methimazole Initiation," Journal of Community Hospital Internal Medicine Perspectives: Vol. 16: Iss. 2, Article 13.
DOI: 10.55729/2000-9666.1579
Available at: https://scholarlycommons.gbmc.org/jchimp/vol16/iss2/13

DOI

10.55729/2000-9666.1579