Angioedema
ICD-10 D84.1; L56.3 · ICD-11 EB01.Y

Treatment of Angioedema in Hereditary Angioedema with Recurrent Episodes and C4 Complement Below 50%

Clinical Scenario

This protocol covers hereditary angioedema (HAE) — an autosomal dominant disorder characterised by recurrent bouts of swelling primarily affecting the extremities, gastrointestinal tract, and genitalia. A C4 complement level below 50% supports the diagnosis in this population.

Defining Condition

Patients present with recurrent acute angioedema episodes at the extremities, within the gastrointestinal tract, and in the genitalia. Complement testing — specifically a C4 level below 50% — is a key diagnostic indicator that helps confirm the hereditary nature of the disorder.

Therapeutic Approach (partial)

For acute, severe episodes in this setting, management involves a blood-product-based intervention. The complete structured regimen — including decision criteria, sequencing, and clinical thresholds — is available in the full protocol.

Full algorithm available below.

Instant Access to Structured Evidence-Based Regimens

References

  1. Hereditary angioedema (HAE) is an autosomal dominant disorder characterized by recurrent bouts of angioedema primarily affecting the extremities, gastrointestinal tract, and genitalia.
  2. A C4 level below 50% suggests the diagnosis.
  3. There are several reports on the successful use of fresh frozen plasma (FFP) for acute exacerbations of HAE.
  4. Consider FFP for acute, severe episodes of HAE.
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