Hereditary angioedema (HAE), also known as C1 inhibitor deficiency, manifests as a deficiency in the amount or function of C1 inhibitors. It is an autosomal dominant disorder with an incidence of 1/10,000- 1/50,000. The clinical manifestation is recurrent cutaneous and submucosal edema. The clinical manifestations of cutaneous edema are as follows: 1) episodic: variable episodes; 2) limited: frequent on the face, extremities, and external genitalia; 3) self-limiting: usually lasts 2-3 days and resolves spontaneously; 4) asymmetric: mostly occurs on unilateral extremities; 5) not painful, not itchy, not accompanied by urticaria, and ineffective with antihistamines or corticosteroid therapy. Oral mucosal edema is characterized as follows: when edema occurs in the upper respiratory tract, it is manifested as laryngeal edema, and death by asphyxiation may occur if treatment is not timely; when edema occurs in the gastrointestinal tract, it is manifested as symptoms of acute intestinal obstruction with a small amount of ascites, which is often misdiagnosed and mistreated, and even performed by dissection. Minor trauma, intraoral operations and emotional changes often induce edema attacks. Diagnosis is based on 1) family history: 75% of patients have a family history and another 25% have no family history; 2) clinical manifestations; 3) laboratory tests: mainly complementology tests, which show reduced CH50 and C4 levels. The characteristic tests are reduced levels of C1 inhibitor (type I) or normal C1 inhibitor concentration with abnormal function (type II). In a small number of patients, occurring only in females in families, both the concentration and function of C1 inhibitor are normal (type III). C1q levels are normal in all of the above types of patients. Treatment Acute exacerbation treatment: there are no effective drugs in China. If laryngeal edema occurs, immediate hospitalization for observation and corresponding treatment; if severe laryngeal edema makes tracheal intubation impossible, tracheotomy should be performed immediately; if conditions are not available, cricothyroid puncture with a thick needle can be performed first, followed by formal tracheotomy; if there are no more exacerbations within 2 months, and CH50 and C4 have both approached normal, consideration can be given to extubation. In Europe, C1 inhibitor biologics have been available for more than 20 years, and the symptoms can be relieved after 30 minutes to 1 hour of intravenous input. Long-term prophylaxis: Danazol is the most commonly used drug at home and abroad, and the maintenance dose varies from 50-600 mg/day depending on the condition. Short-term prophylactic treatment: In China, Danazol is mostly given orally 3 times a day at 200mg for 10 days before surgery, and continued to be applied for 10 days after surgery, and the dose can be gradually reduced to discontinuation if there is no attack. In Europe, 500-1500 U C1 inhibitor before surgical operation.