Acquired C1 inhibitor (C1-INH) deficiency with consequent
angioedema is a rare condition that may indicate an underlying
lymphoproliferative disorder. The defect is caused by increased catabolism, which is often associated with the presence of serum
autoantibodies to C1-INH. The present report describes 3 patients with
systemic lupus erythematosus who developed typical symptoms of
acquired angioedema, characterized by recurrent swelling of subcutaneous and mucous tissues. The 3 patients demonstrated a major classical pathway-mediated
complement consumption, with very low levels of C3
antigen and decreased levels of C1-INH
antigen. Neither
antibodies to C1-INH nor associated lymphoproliferative disease was found. No patient had clinical and
biologic signs of lupus activity at the time the
angioedema occurred. All patients were treated with
steroids and exhibited a good response, without relapse of
angioedema and with normalization of plasma levels of C1-INH. In lupus patients who present with an
angioedema syndrome, acquired or
hereditary angioedema must be sought by examining parameters of the classical pathway and levels of C1-INH. Our observations suggest the existence of a new form of acquired C1-INH deficiency associated with a major classical pathway-mediated
complement consumption and systemic autoimmunity.