Hereditary Angioedema

Hereditary angioedema (C1 inhibitor deficiency, OMIM: 106100) is a genetic disease of the immune system with autosomal dominant inheritance. This is not a classic immunodeficiency, in which the affected individual would be exposed to a higher risk of infectious disease, but it is a hereditary disease of the immune system, where a mutation in the gene for one of the components of the immune system damages its carrier.

Pathogenesis
The mutation affects the complement component C1 inhibitor gene (C1-INH, localization 11q11-q13.1). The product of the mutated gene is either not formed at all or is non-functional. This means that every stimulus (albeit minimal and harmless such as a minor injury) leads to the activation of the entire complement cascade, the clinical manifestations are responsible for increased bradykinin production, which is normally regulated by inhibition of prekallikrein to kallikrein conversion by C1-INH.

Clinical picture
Externally, the disease manifests itself in swelling of the subcutaneous tissue and mucous membranes, which are pale, itchy, without a local increase in temperature. Swelling of the mucous membranes of the respiratory tract can be dangerous, gastrointestinal mucosa can cause indigestion, in severe form pain and partial intestinal obstruction and mimic a sudden abdominal event, urinary tract mucosa is at risk of urinary retention.

The disease has a later onset, sometimes in adulthood.

Diagnosis
The diagnosis is based on the demonstration of low levels of the C4 component of complement (due to consumption) and very low (in the non-functional form of C1-INH also normal or high) levels of C1-INH.

Differential diagnosis
It is necessary to differentiate the acquired forms differentially - paraneoplastic (consumption of C1-INH in tumor tissue), parainfectious (rarely in Hellicobacter pylori infection) and drug (in ACEI therapy up to 0.3−1 %)

Therapy
The B2R receptor antagonist bradykinin is used in acute treatment.- icatibant s.c. and i.v. C1-INH substitution. Antifibrinolytics (tranexamic acid) and danazol (ethinyltestosterone derivative) are used for long-term prophylaxis.