Hereditary angioedema (HAE) is frequently misdiagnosed as drug allergy. It is essential to differentiate HAE from allergy. Diagnosing HAE-normal-C1INH (conventional HAE type III), presenting normal C1-INH, is even more difficult. Here, we report a case of a 17-year-old female diagnosed with HAE and having labeled wheat and multiple drug allergies. She had been suffering from skin edema and abdominal symptoms since childhood. After taking wheat at 13 years old, she had multiple episodes of the same symptoms. Wheat allergy was suspected, and she started eliminating wheat. Multiple attacks were observed after several drug use, and drug allergy was labeled. However, her attacks did not improve after eliminating wheat and the suspected drugs. Her C4 and C1-INH activity was normal, but we diagnosed her with HAE-normal-C1INH based on her family history, multiple attacks after dental procedures, ineffective antihistamines, and significant efficacy of C1-INH infusion. A double-blind, placebo-controlled wheat challenge test at our hospital was negative, and wheat removal was lifted. Drugs could be de-labeled by allergic tests and history. Repeated attacks of unexplained edema and abdominal pain should be differentiated from HAE and lead to an appropriate diagnosis.
Keywords: drug allergy; food allergy; hereditary angioedema; oral food challenge.