High prevalence of anti-C1q antibodies linked to renal involvement in IgG4-related disease
Aanti-C1q antibodies are highly prevalent in IgG4-related disease (IgG4-RD), especially in patients with renal involvement and cutaneous small-vessel vasculitis (CSVV), supporting the role of immune complex-mediated complement activation in the disease’s pathogenesis, according to a study.
Researchers evaluated 70 patients with IgG4-RD. Anti-C1q antibodies were detected in 74.3% of participants, with higher levels observed in those with active disease. Renal involvement was significantly more common among patients with positive anti-C1q antibodies, while CSVV was present in 8.6% of the cohort, all of whom tested positive for these antibodies.
Patients with CSVV displayed palpable purpura, multi-organ involvement, and elevated levels of IgG, IgG1, IgG4, and serum free light chains. Skin biopsies confirmed leukocytoclastic vasculitis with lymphocytic and eosinophilic infiltrates. Anti-C1q levels correlated negatively with C3 and C4 levels, while positively associating with IgG subtypes.
Reference
Martín-Nares E, Nuñez-Álvarez CA, Hernández-Molina G. Anti-C1q antibodies in IgG4-related disease are common and associated with renal involvement and cutaneous small-vessel vasculitis. Rheumatology (Oxford). 2025;keaf020. doi: 10.1093/rheumatology/keaf020. Epub ahead of print. PMID: 39798124.