hereditary C2 deficiency
References
Jonsson G, Sjoholm AG, Truedsson L, Bengtsson AA, Braconier JH, Sturfelt G. Rheumatological manifestations, organ damage and autoimmunity in hereditary C2 deficiency. Rheumatology (Oxford). 2007 Jul;46(7):1133-9. PMID: 17478473