Angioedema is the swelling of skin, subcutaneous, or submucosal tissue due to acquired or genetic causes.
Angioedema is swelling of skin, subcutaneous and submucosal tissues and can be acquired or genetic. In genetic angioedema, SERPING1 and F12 genes are involved. Acquired angioedema can be due to drugs, allergy or burns. The main mechanism of swelling in angioedema is the activation of bradykinin which is a potent vasodilator. The patients usually present with swelling of face and hands. In severe cases, respiratory distress can occur.
Hereditary angioedema: Occurs due to an autosomal dominant gene mutation. The genes include the SERPING1 gene and F12 gene. Both of these genes lead to pathological activation of complement pathway.
Acquired angioedema: Acquired angioedema can result from the following causes:
Angioedema is the swelling of subcutaneous tissues and mucosa due to accumulation of fluid  . It results from various stimuli that cause the release of bradykinin  . In addition to being a potent vasodilator, bradykinin also facilitates the extravasation of fluid from the blood vessels. Intravascular fluid therefore starts accumulating extravascularly leading to the swelling. The skin around the eyes is the loosest skin of the body; therefore, the fluid accumulate there first and later other area of the face also succumb to swelling.
Angiotensin converting enzyme (ACE) normally causes the breakdown of bradykinin in the body. However, when ACE inhibitors are used, bradykinin breakdown is suppressed and angioedema can develop.
In hereditary angioedema, there is a decreased production of C1-INH which leads to the activation of the complement system  . This unopposed activation of complement system results in the continuous production of bradykinin. In autoimmune angioedema, antibodies are formed against C1-INH and bradykinin is similarly increased.
In addition, some agents such as alcohol and some drugs (such as ibuprofen and aspirin) can increase the incidence of angioedema .
Early recognition of angioedema and aggressive treatment results in a very good prognosis. Early intubation with endotracheal tube lead also improves the prognosis by limiting the respiratory distress. If the treatment is delayed, it may even prove fatal for the patient.
In hereditary angioedema, the patients present with swelling that develops 2 to 5 hours after any stimulus such as a minor trauma or infection. The swelling can involve any part of body and is often associated with rashes. The patients frequently experience abdominal symptoms such as nausea, vomiting, abdominal pain and diarrhea. The patients usually have one episode of attack per month. Some patient may have a higher frequency of attacks Attacks usually last from 12 to 48 hours.
In acquired angioedema, the predominant feature of angioedema is swelling of the face, mucous membranes and hands. Swelling may be itchy and associated with skin rash. Sensations of the skin can be decreased due to extravasation of fluid that causes compression of the nerves. If the swelling of the mucus membranes of the upper respiratory tract is severe, respiratory distress along with cough and wheezing may occur . The patient is unable to breathe which leads to rapid decrease in the oxygen concentration in the arterial blood. If this is not treated promptly, permanent brain damage may occur.
The diagnosis of angioedema can often be made on clinical grounds. Certain investigations are helpful in confirming the diagnosis and etiology of this disease. Mast cell tryptase levels are raised in the patients suffering from angioedema. However, unlike other allergic conditions, there is no response to therapy with antihistaminic and steroidal drugs.
In hereditary angioedema, there is often a typical family history. In addition, the deficiency of C2 and C4 component of the complement system is present. In patients with F12 gene mutation, the diagnosis is done by excluding other types of angioedema.
The treatment of angioedema depends upon the etiology.
Angioedema means the swelling of the skin and underlying tissue because of the collection of fluid. It can result from genetic causes or from acquired causes. The patients usually develop swelling of the face, arms and hands. Sometimes, swelling may involve the upper respiratory tract which leads to breathing difficulties. Emergency management may be indicated in such cases. The treatment depends upon the cause but the overall prognosis is good.