Complement, coagulation and fibrinolytic parameters in hereditary angioedema (HAE)

Area of Science:

• Hematology
• Immunology
• Biochemistry

Background:

• Hereditary angioedema (HAE) is characterized by severe deficiency of C1 inhibitor (C1 INH).
• The intrinsic clotting, kinin generation, and fibrinolytic systems are crucial for hemostasis and inflammation.
• Understanding the interplay of these systems in HAE is essential for managing the condition.

Purpose of the Study:

• To investigate the status of the intrinsic clotting, kinin generating, and fibrinolytic systems in patients with hereditary angioedema (HAE).
• To determine if the lack of C1 INH in HAE patients affects these coagulation and fibrinolytic pathways.
• To elucidate the compensatory mechanisms, if any, that prevent hyperactivation of these systems in HAE.

Main Methods:

• Comparative analysis of plasma samples from 10 HAE patients, 10 chronic urticaria patients, and 18 healthy volunteers.
• Assays to evaluate the intrinsic clotting system, kinin generation pathway, and fibrinolytic system.
• Measurement of plasma kallikrein, HMW-kininogen, Factor XII levels, and pre-kallikrein activation rates.

Main Results:

• Despite severe C1 INH deficiency, HAE patients did not exhibit impaired intrinsic coagulation or fibrinolytic systems.
• A slight decrease in plasma kallikrein and a more significant decrease in HMW-kininogen were observed in HAE patients.
• Factor XII levels were increased, and pre-kallikrein activation was delayed in HAE patients compared to controls.

Conclusions:

• Lowered HMW-kininogen levels in HAE patients appear to compensate for the C1 INH deficiency.
• This compensation mechanism effectively prevents enhanced activation of the intrinsic clotting and fibrinolytic systems.
• The findings highlight a complex interplay between C1 INH, HMW-kininogen, and coagulation/fibrinolysis in HAE pathogenesis.