What should you know about angioedema C1 inhibitor?

Swelling can affect the face, lips, hands, feet, genitals, bowel wall, or airway. Episodes often occur without itchy hives, and standard allergy medicines may have little effect when bradykinin is the driver.

C1 inhibitor is a protein that restrains several inflammatory pathways. When the protein level is low or it does not work properly, excess bradykinin can make small blood vessels leak fluid into deeper tissues. The resulting swelling is called C1-inhibitor–related angioedema.

The problem may be inherited or acquired later in life. A clinician may use the pattern of attacks, family history, medication history, and complement blood tests to distinguish these forms from histamine-mediated angioedema. The absence of a known family history does not rule out an inherited form.

Arrange a medical assessment for recurrent swelling without hives, unexplained severe abdominal attacks, or swelling that does not improve as expected with allergy treatment. Record the body area involved, possible triggers, medicines taken, accompanying hives or itching, and how the episode resolved.

If C1-inhibitor–related angioedema is confirmed, ask for a written plan covering treatment for an acute attack, medicine access, procedures or dental work, travel, and whether preventive therapy fits your pattern. Do not stop a prescribed medicine on your own; instead, review any suspected trigger with the prescriber.

Call emergency services immediately for tongue or throat swelling, a changed or hoarse voice, noisy breathing, trouble breathing, difficulty swallowing, drooling, faintness, or rapidly worsening facial or neck swelling. Use any prescribed on-demand treatment as directed, but do not delay emergency help while waiting for it to work.

Severe or persistent abdominal pain, repeated vomiting, marked abdominal swelling, or inability to keep fluids down also warrants prompt assessment. Tell the emergency team if C1-inhibitor deficiency or bradykinin-mediated angioedema has been diagnosed or suspected.

Ask which blood tests are appropriate, whether results should be repeated when you are well, and whether your history suggests an inherited or acquired cause. If an inherited form is diagnosed, discuss which relatives should be offered assessment.

Clarify which medicine to use at the first sign of an attack, how to store and carry it, what to do before medical or dental procedures, and which symptoms require emergency care even after treatment.