Overview
C1 inhibitor deficiency, now more commonly referred to as hereditary angioedema (HAE), is a condition where the body either does not make enough of a protein called C1 inhibitor (C1-INH) or makes a form of it that does not work properly. This protein plays an important role in controlling inflammation and the immune system's complement pathway. When C1 inhibitor is missing or not functioning, it leads to episodes of severe swelling (called angioedema) that can affect the face, hands, feet, arms, legs, throat, and the lining of the gut. Swelling in the throat can be life-threatening because it may block the airway. Abdominal attacks can cause intense pain, nausea, vomiting, and diarrhea, and are sometimes mistaken for a surgical emergency. There are different types of this condition. Type I involves low levels of C1 inhibitor protein, while Type II involves normal levels of a dysfunctional protein. An acquired form also exists, usually appearing later in life and linked to other underlying conditions like lymphoma. The treatment landscape has improved significantly in recent years, with several FDA-approved therapies now available for both prevention and treatment of acute attacks. These include plasma-derived C1 inhibitor concentrates, a kallikrein inhibitor called lanadelumab, and icatibant, a bradykinin receptor blocker. Early diagnosis and having an emergency action plan are essential for managing this condition safely.
Key symptoms:
Recurrent episodes of severe swelling of the skinSwelling of the face, lips, or eyelidsSwelling of the hands and feetThroat swelling that can make breathing difficultSevere abdominal pain from swelling in the gut liningNausea and vomiting during abdominal attacksDiarrhea during abdominal attacksSwelling that does not respond to antihistamines or steroidsSwelling episodes that last 2 to 5 days without treatmentA tingling or tight sensation before swelling beginsFatigue during and after attacksSkin rash that is not itchy (erythema marginatum) before some attacks
Autosomal dominant
Passed on from just one parent; each child has about a 50% chance of inheriting it
Variable
Can begin at different ages, from infancy through adulthood
Treatments
No FDA-approved treatments are currently listed for OBSOLETE: C1 inhibitor deficiency.
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Specialists
View all specialists →No specialists are currently listed for OBSOLETE: C1 inhibitor deficiency.
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to OBSOLETE: C1 inhibitor deficiency.
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Caregiver Resources
NORD Caregiver Resources
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Mental Health Support
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.What type of C1 inhibitor deficiency do I have (Type I, Type II, or acquired)?,Should my family members be tested for this condition?,What rescue medication should I carry at all times, and how do I use it?,Am I a candidate for long-term preventive therapy to reduce the number of attacks?,What should I do if I experience throat swelling or difficulty breathing?,Are there medications or situations I should avoid that could trigger an attack?,How should we plan for dental procedures, surgeries, or pregnancy?
Common questions about OBSOLETE: C1 inhibitor deficiency
What is OBSOLETE: C1 inhibitor deficiency?
C1 inhibitor deficiency, now more commonly referred to as hereditary angioedema (HAE), is a condition where the body either does not make enough of a protein called C1 inhibitor (C1-INH) or makes a form of it that does not work properly. This protein plays an important role in controlling inflammation and the immune system's complement pathway. When C1 inhibitor is missing or not functioning, it leads to episodes of severe swelling (called angioedema) that can affect the face, hands, feet, arms, legs, throat, and the lining of the gut. Swelling in the throat can be life-threatening because it
How is OBSOLETE: C1 inhibitor deficiency inherited?
OBSOLETE: C1 inhibitor deficiency follows a autosomal dominant inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.