Concomitant Polymyalgia Rheumatica and Giant Cell Arteritis Associated with Cystic Echinococcosis: A Rare Geriatric Case.

Introduction: Parasitic infections could be an important triggering factor for autoimmune diseases. We present a clinical case of concomitant polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) induced with cystic echinococcosis (CE).

Case Presentation: A 74-year-old male was admitted with a 2-month history of progressive pain at the shoulders and hip, movement restriction, and constitutional symptoms. As a result of the examinations performed due to rheumatological complaints, PMR and GCA were diagnosed. The cystic appearance, which was incidentally detected in the liver 6 months ago and not examined at that time, was found to be hydatid cyst. Medical treatment was initiated for all three conditions and the patient's symptoms improved significantly.

Discussion: Parasite infections may cause various autoimmune diseases because of molecular mimicry or sustained immune activation. Echinococcus granulosus is a very complex multicellular parasite and highly immunogenic for humans. Some body parts of the parasite, the outer surface and secreted particles, stimulate the host immune system strongly.

Conclusion: The first case in the literature of coexistence of PMR and GCA associated with CE. Autoimmune diseases should be evaluated in patients with CE. Furthermore, CE should be considered in patients with autoimmune diseases in the presence of a cyst.