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The Physician's Guide to Laboratory Test Selection and InterpretationHereditary Angioedema
Hereditary angioedema (HAE) is an episodic swelling disease associated with the deficiency of C1-esterase inhibitor.
Epidemiology
- Incidence – defect is rare
- Age – onset usually in childhood
- Gender – equal gender distribution
Risk Factors
- Genetics
- Autosomal dominant inheritance
- Pressure applied to an extremity
- Stress
Pathophysiology
- C1-esterase inhibitor (C1-INH) is a multispecific, protease inhibitor
- It regulates the enzymes of the complement, coagulation, fibrinolytic and kinin-forming systems, including:
- C1r and C1s subunits of activated first component of complement
- Activated Hageman factor (factor XIIa) and Hageman factor fragments
- Activated plasma thromboplastin antecedent (PTA or factor XIa)
- Kallikrein (Fletcher factor)
- Plasmin
- HAE is a quantitative deficiency in C1-INH
- Types include null (type 1) and dysfunctional (type 2)
- Deficiency of functionally active component may lead to life-threatening angioedema
- Rare type 3 defect associated with similar clinical presentation but normal C1-INH levels
- Acquired C1-INH deficiency is a qualitative (functional) deficiency of inhibitor
Clinical Presentation
- Acquired deficiency is associated with a variety of diseases, including lymphoid malignancies
- Transient, but recurrent attacks of non-pruritic, deep-seated swelling of various tissues occur throughout the body
- Gastrointestinal tract often involved, with recurrent episodes of cramping abdominal pain
- Most frequent cause of death is airway obstruction secondary to laryngeal edema
Diagnosis
- Laboratory testing
- HAE – C-1-Esterase Inhibitor levels
- Acquired deficiency – functional assays
Treatment
- Therapy for congenital defect is androgen treatment which partially corrects the biochemical defect
- Aminocaproic acid may be used for preoperative prophylaxis
- Aminocaproic acid contraindicated in patients with thrombotic tendencies
