A new type of acquired C1 inhibitor deficiency associated with systemic lupus erythematosus

Acquired C1 inhibitor (C1-INH) deficiency with consequent angioedema is a r are condition that may indicate an underlying lymphoproliferative disorder. The defect is caused by increased catabolism, which is often associated wi th the presence of serum autoantibodies to CI-INH. The present report descr ibes 3 patients with systemic lupus erythematosus who developed typical sym ptoms of acquired angioedema, characterized by recurrent swelling of subcut aneous and mucous tissues. The 3 patients demonstrated a major classical pa thway-mediated complement consumption, with very low levels of C3 antigen a nd decreased levels of C1-INH antigen. Neither antibodies to C1-INH nor ass ociated lymphoproliferative disease was found. No patient had clinical and biologic signs of lupus activity at the time the angioedema occurred. All p atients were treated with steroids and exhibited a good response, without r elapse of angioedema and with normalization of plasma levels of C1-INH. In lupus patients who present with an angioedema syndrome, acquired or heredit ary angioedema must be sought by examining parameters of the classical path way and levels of C1-INH. Our observations suggest the existence of a new f orm of acquired C1-INH deficiency associated with a major classical pathway -mediated complement consumption and systemic autoimmunity.