Hereditary angioedema type 1 in a 39-year-old woman with a three-generation pedigree: a case report

Background Hereditary angioedema (HAE) is a rare autosomal dominant genetic disorder, clinically manifested as recurrent localized edema of the skin and mucous membranes, which can involve the gastrointestinal tract and cause severe abdominal pain when present. It is often misdiagnosed as gastroenteritis or allergic diseases. Objective To report a case of a patient with long-term misdiagnosis of HAE and the family situation, in order to enhance the clinical understanding of this disease. Method The patient's medical history and family history were collected, and laboratory tests were conducted, including the determination of complement C4, C1 esterase inhibitor (C1-INH) concentration and function. Result The patient was a 39-year-old female who had recurrent skin and mucous membrane edema accompanied by abdominal pain for 9 years. She had been misdiagnosed as gastroenteritis and allergy. Ten members of the family had similar attack histories. Laboratory tests showed that Complement C4: 0.01g/L (normal range 0.1-0.4g/L). C1-INH concentration (nephelometry): <0.03g/L (normal range 0.21-0.39g/L). C1-INH function test (ELISA): 1.7% (normal range ≥68.0%). Based on typical clinical manifestations, family history, and significantly reduced C1-INH concentration and function, the final diagnosis was HAE-1 type. Conclusion For unexplained episodic edema, especially when there is a family aggregation history, early detection of C4, C1-INH concentration and function should be conducted to make a clear diagnosis. This case emphasizes the importance of including HAE in the differential diagnosis of recurrent abdominal pain and edema to reduce misdiagnosis and improve patient prognosis.