What is the difference between hereditary angioedema (HAE) type I, II and III?

HAE type I

Autosomal dominant. 85% of the C1 esterase deficiencies. Impairment of mRNA transcription or translation which leads to decreased C1 esterase enzyme synthesis.

HAE type II

Autosomal dominant. Production of an inactive protein.

HAE type III

Estrogen-dependent -- all female. Normal C1 INH level and function and normal C4.

C1 protein, showing subunits C1r, C1s, and the C1q tails. Image source: Wikipedia.

Classical and alternative complement pathways. Image source: Wikipedia.

Angioedema (AE) can be allergic or non-allergic.

There are 5 types of non-allergic angioedema (AE):

- acquired AE
- hereditary AE (HAE)
- ACE-inhibitor induced AE
- idiopathic AE, can occur with chronic urticaria
- pseudoallergic AE, e.g. reaction to NSAIDs

There are 3 types of HAE that are differentiated by C4 and C1-INH levels

- type I HAE - low C4, low C1-INH function, low C1-INH antigen level
- type II HAE - low C4, low C1-INH function, normal C1-INH antigen level
- type III HAE - all normal

Treatment of acute HAE attacks

- C1-INH, 20 units/kg, IV infusion
- Icatibant, 30 mg SC, bradykinin B2 receptor antagonist
- Ecallantide, 30 mg SC, kallikrein receptor antagonist

Prophylaxis of HAE attacks

- C1-INH, 1,000 units, IV infusion every 3-4 days
- attenuated androgen, e.g. danocrine 200 mg PO TID


C1 Esterase Inhibitor Deficiency. 5-Min Clinical Consult. Unbound Medicine, Inc.
New Directions in the Treatment of Angioedema. Medscape, 2012.

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