The Halo Sign on Cardiac MRI in Recurrent Pericarditis

Recurrent pericarditis can be difficult to manage. We describe the halo sign, a circumferential or regional rim of increased pericardial signal on T2-weighted imaging and/or late gadolinium enhancement (LGE), and its evolution during rilonacept therapy. Three patients with idiopathic, postcardiac injury, and autoimmune recurrent pericarditis underwent serial cardiac magnetic resonance (CMR). Baseline CMR demonstrated the halo sign with concurrent edema and LGE. Edema resolved with near-complete LGE regression in the idiopathic and postcardiac injury cases, permitting therapy discontinuation without recurrence. The autoimmune case showed persistent edema and LGE at 1 year, with improvement by 2 years. Serial CMR demonstrated treatment response. Concurrent edema and LGE suggested active inflammation, whereas isolated LGE may reflect chronic inflammatory remodeling, neovascularization and/or fibrosis. The halo sign provides a simple descriptive framework for pericardial inflammation. Serial CMR, integrated with clinical findings and biomarkers, may distinguish active inflammation from chronic inflammatory remodeling and guide individualized therapy.