[A CASE OF HEREDITARY ANGIOEDEMA WITH NORMAL C1 INHIBITOR (HEREDITARY ANGIOEDEMA TYPE III) WITH A PATHOGENIC VARIANT...

Hereditary angioedema (HAE) is a rare genetic disease characterized by recurrent episodes of temporary organ swelling. Here, we report a case of HAE type III who experienced recurrent acute abdominal pain after starting low-dose estrogen therapy. Genetic analysis by Sanger sequencing led to the identification of a recurrent heterozygous missense variant c.988A>G (p.K330E) in the plasminogen (PLG) gene of the patient. This variant was previously found in her elder sister who also had the disease. She was treated with tranexamic acid as a long-term prophylactic. Her attacks did not increase during her pregnancy. We managed the patient with intravenous injection of C1-INH preparation before and after delivery. As the frequency of attacks increased after delivery and after the resumption of menstruation, the dose of tranexamic acid was increased, and a subcutaneous injection of lanadelumab was started.While the severity of attacks reduced, she experienced the attacks once or twice a month. After switching from lanadelumab to twice-weekly subcutaneous injections of C1-inhibitor (C1-INH), she had no attacks requiring additional treatment, although she had several minor attacks. To establish appropriate treatment for HAE type III, accumulation of cases, determination of the causative gene in each case, and elucidation of the pathology are warranted.