Angioneurotic edema refers to swelling of the deep dermis or subcutaneous tissues involving the mucous membranes and tissues of the eyes, lips, genitalia and extremities.

Angioedema has become the most common allergic disorder resulting in hospitalization.

Hereditarily angioneurotic edema is a rare genetic disorder characterized by repeated extreme swelling of the arms, face, feet, hands, gastrointestinal tract, and upper airways.

Hereditary angioedema is a rare or somatic dominant disorder that affects approximately one and 50,000 persons worldwide.

The mean, age of onset of hereditary angioedema is 8 to 12 years, and symptoms often worsen during puberty.

Hereditary angioedema leads to unpredictable, disabling, and potentially fatal swellings.

Symptoms often first appear during childhood, with attacks occurring in patients throughout their lifetime.

Attacks of swelling of primarily G.I. tract and cutaneous and subcutaneous tissues of the body.

Angioedema attacks may occur as frequently as every several days and can last a few hours to several days.

Laryngeal edema can be life-threatening.

Triggers include emotional distress, physical, trauma, infections, physical exertion, surgery, and other medical procedures.

The fundamental abnormality in hereditary angioedema is a deficiency of functional C1 inhibitor due to a mutation in the SERPING1 gene which regulates multiple proteases involved in the complement, contact system, coagulation, and fibrinolytic pathways.

The symptoms of hereditary angioedema result from the dysregulation of the contact activation pathway.

C1 esterase inhibitor is a key regulator of the pathway, and attenuates the production of bradykinin, a peptide, that leads to increased vascular permeability, and subsequent tissue swelling, by means of the inhibition of the proteases factor XIIa and plasma kallikrein.

C1 inhibitor inactivates plasma kallikrein, factor XIIa  and factor 12f.

The fundamental defect in most cases of hereditary angioedema, is deficiency of a functional C1 inhibitor protein, a protease that belongs to the superfamily of serene, protease inhibitors.

The majority of cases of Hereditary angioedema are caused by either decreased levels or reduced functionality of C1 inhibitor.

C1 inhibitor has a crucial role in regulating complement, contact, system, coagulation, and fibrinolytic pathways.

A lack of C1 inhibitor results in unregulated activation of plasma, proteolytic cascades, that generate bradykinin, the principal, vasoactive peptide responsible for swelling in hereditary angioedema.

Plasma kallikrein is directly responsible for the cleavage of bradykinin from a high molecular weight kininogen and is a therapeutic target for the treatment and prevention of angioedema attacks.

Angioedema attacks result from uncontrolled activity of contact system components factor XIIa and plasma kallikrein, which leads to excessive bradykinin release and subsequent locally increased vascular permeability.

The majority of hereditary angioedema cases are caused  by either decreased levels or reduced functionality of C1 esterase inhibitor.

The contribution of kallikrein to the formation of hereditary  attacks renders it and its precursor plasma pre-kallikrein  targets for prophylaxis.

Mutations in hereditary type 1 HA include: missense, nonsense, deletion or insertion, or splicing defects resulting in a truncated or misfolded C1 inhibitor that it is not efficiently secreted.

In HA type II the defect is a missense mutation in exon 8 interfering with the ability to inhibit target proteases, with rare exceptions.

C1 inhibitor threshold functional level in HA to control plasma contact system is approximately 40%.

C1 inhibitor deficiencies levels in HA I is generally 5-30% of the normal level. 

Rare, life-threatening disorder characterized by cutaneous and submucosal swelling.


It is a physical manifestation of transient increase in vascular permeability.

The hallmark symptom in hereditary angioedema is localized swelling of the skin submucosal tissue in the face, lips, throat, hands, feet, or genitalia that is nonpitting, nonpruritic, and not accompanied by urticaria.

Despite the interaction of an activated plasma contact and fibrinolytics systems, such  patients do not appear to be at increased rate risk for bleeding or thrombosis.

Fundmental defect is a deficiency of C1 inhibitor protein.


The majority of cases of HA are caused by genetic mutations that lead to deficiency (type I) or dysfunction (type II) of C1 esterae inhibitor, a serine protease inhibitor that regulates multiple pathways, including the kallikrein-kinin and contact system.


In a very rare third type of HA, patients have normal levels of functional C1-I NH and often have a distinct clinical presentation, including a higher frequency of facial, pharyngeal , and tongue swelling


Typical swelling in HA is caused by locally increased vascular permeability in response to excessive bradykinin formation, which resulted from inadequate control of the contact system components Factor XIIa and plasma kallkriein.

Activation of the plasma contact system generates bradykinin.

The bradykinin B2 receptor is expressed on endothelial cells and is felt to be the principally responsible for the active transfer of fluid into localized tissues, with resultant angioedema.

Abdominal pain can be the sole symptom in attack of angioedema.


Abdominal attacks can occur and up to 49% of episodes.

Laryngeal edema occurs in approximately 0.9% of attacks and may be life-threatening.

Some patients report prodromal symptoms.

Up to half of patients have a characteristic serpiginous rash and other symptoms include fatigue, transient numbness or tingling, at the site of large swelling.

Can be a debilitating disease that negatively affects work, school, and travel.

Airway swelling and respiratory obstruction are potentially life-threatening due to asphyxiation.

Associated gastrointestinal tract swelling cases present as severe abdominal pain, nausea, and vomiting.

Generally self limiting localized swelling of the skin and mucosal membranes that can last up to 72 hours.

Cutaneous attacks of angioedema without urticaria with spontaneously remitting and severe abdominal symptoms of pain and swelling should alert clinicians to consider hereditary angioedema diagnosis.

Rarely patients may have genital bladder, muscle or joint swelling. 

Laryngeal episodes account for approximately 0.9% of all attacks and more than 50% will have a laryngeal attack during their lifetime.

Overall lifetime incidence is approximately 10-15%.

Can be acute or chronic, is usually transient, but often recurrent in nature.

Tends to involve loose connective tissue such as the face, lips, mouth, throat, and larynx.

Two types acquired and hereditary.

Caused by mutations of the C1 esterase-inhibitor gene, with reduced activity/quantity of the protein.

The majority of cases of hereditary angioedema are caused by genetic mutations that lead to deficiency or dysfunction of C1 esterase inhibitor a serine protease inhibitor that regulates multiple pathways, including the kallikrein-kinin contact system.
C1 esterase inhibitor is a major inhibitor of plasma kallikrein and coagulation factor XIIa.

C1  inhibitor protein is a protease inhibitor in the serpin  family and bradykinin is the biological mediator of swelling.

Decreased levels of C1 esterase inhibitor in HA leads to increase in kallikrein activity, and results in increased levels of bradykinin.

Bradykinin a vasodilator that increases vascular permeability of capillary endothelium resulting in tissue swelling.

Bradykinin is generated by activation of the plasma contact system.


The plasma contact system comprises coagulation factors XII, plasma pre-kallikrein , and high molecular weight kininogen.


Plasma pre-kallikreinand high molecular weight kininogen  circulate as a 1:1  but as a Biomolecular complex.

Acquired type usually idiopathic, allergic, related to medications, a manifestation of autoimmune disease or associated with a lymphoproliferative disorder.

More common forms are allergic or idiopathic and may occur with and without urticaria.

Angioedema induced by angiotensin converting enzyme inhibitors in up to 0.68% of patients who receive ACE inhibitors.

Hereditary angioedema caused by mutations affecting the C1 inhibitor gene resulting in either loss of the C1 inhibitor protein or loss of its function.

Hereditary angioneurotic edema (HAE) occurs in approximately 1 in 10,000 to 50,000 individuals.

Children have a 50% chance of genetically inheriting HAE; however, 25% of HAE cases are linked to spontaneous genetic mutations.

There are 3 types of HAE, none of which respond to antihistamine or corticosteroid therapy.

In types 1 and 2 HAE, patients have a genetic defect with a loss of C1-inhibitor control and produces characteristic swelling.

Type 1 HAE is characterized by low C1-inhibitor levels due to gene defects on chromosome 11.

Type 2 HAE is characterized by normal to low C1-inhibitor levels, and inhibitors that are present are dysfunctional.

Type 3 HAE research is characterized by normal C1-inhibitor levels and function.

Hereditary angioedema type presents with recurrent, circumscribed episodes of tissue or mucous membrane swelling which is self-limiting.

Hereditary angioedema autosomal dominant transmission resulting from deficiency of C1-INH (C1 inhibitor gene).

Hereditary angioedema associated with recurrent episodes on nonpruritic, subcutaneous or submucosa edema which is nonpitting, and which occurs typically on the arms, legs, hands, feet, bowels, genitalia, trunk face larynx or tongue.

Hereditary angioedema symptoms may begin as early as age 2 or 3 years of age, worsens around puberty, and persists throughout life.

Hereditary angioedema severity is unpredictable.

Rare genetic disorder characterized by intermittent acute attacks of edema of the skin and mucous membranes, which may be life threatening.

Autosomal dominant process with estimated prevalence ranging from 1 case in 10,000 to 5 cases in 50,000.

Edema may involve the larynx, face, oropharynx, extremities, genitalia, and gastrointestinal mucosa.

HA with C1 inhibitor deficiency typically it develops in childhood with a mean age of onset of 8-12 years. 

It rarely occurs before age one and usually worsens during puberty. 

The process fluctuates during the patient’s lifetime and may vary among patients of the same genetic kindred. 

An early onset maybe associated with a more severe process.

It is an autosomal dominant disorder with the prevalence of approximately one case per 50,000 persons.

Because of its rarity it is not recognized and patients may be treated with histamine-mediated or mast cell mediated angioedema agents including glucocorticoids, antihistamines, and epinephrine, which are in effective treatments.

Submucosal angioedema of the intestine can appear to be an acute abdomen and result in a necessary surgery.

Delay in diagnosis can be as long as 8-10 years.

Prodromal symptoms include a serpiginous rash, erythema marginatum in approximately 1/3 of patients, and tingling, fatigue, asthenia, and discomfort the side of emerging swelling also can occur.

Triggering factors include primarily stress, medical procedures, surgery, trauma, infections, and fatigue.

Angiotensin-converting enzyme inhibitors, which block bradykinin catabolism are contraindicated because of risk of exacerbating hereditary angioedema.

Exaggerates estrogens are avoided because of their potential for increasing the severity of the disease.

Type 1 HA with C1 inhibitor deficiency accounts for 85% of cases, and type II accounts for 15%.

HA are characterized by low serum C4 levels from activation of the complement cascade, for which C1 inhibitor is a key regulatory protein.

HA type I, has a low antigen and functional C1 inhibitor level.

HA type II have normal antigen levels but low C1 inhibitor function as a result of mutations affecting the reactive loop of the molecule.

Phenotypically angioedema types I and II are indistinguishable.

Treatment in the past including antifibrinolytic agents tranexamic acid or epsilon aminocaproic acid and attenuated androgens such as danazol.

These agents are now considered second line therapies.

May be associated with nausea, vomiting, diarrhea, and abdominal pain.

Presenting symptoms include cost, swelling, itching, and difficulty breathing.

Occasionally involves the gastric and bowel mucosa leading to nausea, vomiting as a result of gastrointestinal tract swelling.

May be associated with laryngeal airway obstruction.

Typically antihistamines, corticosteroids, or epinephrine are not helpful in management.

Hereditary angioedema frequency of attacks range from virtually never to every three days, with an average attack rate of every 7-14 days.

With hereditary angioedema onset of symptoms often occurs during the teenage years.

Urticaria associated angioedema occurs in about 50% of children who have urticaria.

Urticaria associated angioedema occurs in 1-2% of the general population.

Linked to drugs that target the renin-angiotensin-aldosterone system such as angiotensin enzyme inhibitors, and angiotensin receptor blockers.

Compared with beta-blockers, ACE inhibitors, or aliskiren have a 3 fold higher risk for angioedema, and the risk was lower for ARBs than with ACEIs or aliskiren (Toh S et al).

ACE inhibitor related angioedema represents 30 to 40% of all cases seen US EDs..

Most cases of ACE inhibitor related angioedema occur in the first few weeks of treatment.

African-American women have higher incidence of ACE inhibitor angioedema.

Hereditary angioedema occurs in approximately 1 in 10,000-50,000 people.

Estimated 250-400 people in the U.S. have hereditary angioedema type 1.

Hereditary angioedema has similar prevalence in all ethnic groups.

No epidemiological information available for acquired C1INH deficiency.

Mortality may result from laryngeal swelling and subsequent asphyxia.

Urticaria associated angioedema generally a self-limited problem in childhood.

With hereditary angioedema onset of symptoms often occurs during the teenage years.

Urticaria associated angioedema has no sexual preference.

Hereditary angioedema is an autosomal dominant process affecting both sexes.

Hereditary angioedema 3 reported in females only.

Urticaria related angioedema without age differences, while hereditary is more common beyond the teenage years.

An estrogen dependent form is also hereditary.

Anabolic androgens, and anti-fibrinolytic drugs have been used for the prophylactic management of a hereditary angioedema.

C1 inhibitor concentrate (Cinryze) effective in the treatment of acute attacks.

In randomized trials nanofiltered C1 inhibitor concentrate in the management of hereditary angioedema demonstrated a reduction in the duration of a acute attacks, and when used prophylactically the concentrate reduce the frequency of acute attacks (Zuraw BL).

Approved agents include human plasma C1 derived inhibitor, recombinant human C1 inhibitor, icatibant, a bradykinin, receptor antagonist, and ecallantide an kalikrein inhibitor.

In the above study, 40% of patients treated with C1 inhibitor did not have significant relief of symptoms within four hours.

Individuals at higher risk for acute attacks of hereditary angioedema require prophylactic treatment.

Prophylaxis may be given before dental procedures or other procedures that are highly likely to precipitate an acute attack and C1 inhibitor concentrate and fresh frozen plasma may be used for this purpose.

Bradykinin receptor blocker icatibant and kallikrein receptor blockade ecallanide approved for hereditary angioedema.

Lanadelumab-flyo (Takhzyro) approved for the prophylaxis treatment and prevention of hereditary angioedema (HAE) in patients 12 years or older.

Among patients with hereditary angioedema, donidalorsen treatment resulted in significantly lower rate of angioedema attacks than placebo.

Donidalorsen inhibits prekallikrein production, but does not correct insufficiency of C1 inhibitor.

Donidalorsen is an anti-sense oligonucleotide that targets pre-kallikrein messenger RNA.

Inhibitors a kallikrein activity are approved for long-term prophylaxis of hereditary angioedema.

NTLA-2002 experimental treatment leads to robust, dose dependent and durable reductions in total plasma kallikrein levels with a reduction in angioedema attacks-a gene editing therapy based on CRISPR associated proteins targeting the gene encoding kallikrein B1 (KLKB1).


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