Angioneurotic Edema Without C1 Esterase Inhibitor Abnormality: Efficacy of Tranexamic Acid

The document discusses a case of hereditary angioneurotic edema (OAN) without C1 esterase inhibitor deficiency in a 16-year-old girl who experienced recurrent swelling episodes since the age of 7, particularly around large joints, fingers, face, mucous membranes, and tongue, without true urticaria. These episodes, which sometimes included asthenia, malaise, abdominal, or joint pain, increased in frequency with the onset of menstruation and significantly impacted her daily life and quality of life. The symptoms were resistant to antihistamines and corticosteroid therapy. Blood tests showed normal levels of CH50, C3, C4, and both quantitative and functional C1-inh. An extensive evaluation, including immunological tests, was negative. Treatment with tranexamic acid at a dose of 500 mg three times per day led to a dramatic improvement in symptoms within 8 days, reducing the frequency, duration, and intensity of the episodes. This case may represent a form of estrogen-dependent hereditary OAN or another variety of "idiopathic" OAN. The pathophysiology of OAN is not histamine-dependent but involves the complement activation pathway leading to bradykinine formation. The observation highlights the existence of other types of OAN with normal C1-inh and illustrates the therapeutic interest of tranexamic acid in some of these cases.