This is a monocentric, comparative, cross-sectional, case-control study seeking to identify abnormalities of the C5a-C5aR1 axis between a population of patients with active IgG4-associated disease (MAG4) and two control groups: healthy subjects without MAG4 and patients with MAG4 in remission.
age > 18
diagnosis of IgG4-associated disease according to ACR/EULAR 2019 classification criteria (4,5) with a score ≥20.
disease activity score (IgG4-RD Responder Index) ≥2 in at least one affected organ
presence of a differential diagnosis ("IgG4-RD mimicker") or exclusion criterion according to ACR/EULAR 2019 classification criteria (4,5).
systemic corticosteroid treatment ≥5 mg/day ongoing or < 1 month ; Study C5-MAG4_RCAPHM21_0433 Protocol Version 1.1 of 16/01/2024 Page 15 of 41
immunosuppressive therapy ongoing or < 3 months ;
current biotherapy treatment or < 6 months;