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ICD Hub / Diseases of the immune system (D80–D89) / 4A00.14 - Hereditary angioedema
ICD-11

ICD-11 Codes
for 4A00.14 - Hereditary angioedema
Teodor Jurukovski January 1, 1970
Fact checked by: Teodor Jurukovski
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Understanding Hereditary Angioedema (HAE)

Hereditary angioedema (HAE), identified by the ICD-11 code 4A00.14, is a rare genetic disorder. It is characterised by recurrent episodes of severe swelling, known as HAE attacks, which can affect various parts of the body. This condition arises from fluid leaking out of small blood vessels into surrounding tissues. Unlike other forms of angioedema, HAE typically does not involve itchy hives or urticarial weals. The underlying cause is often a genetic deficiency or dysfunction of a plasma protein called C1 inhibitor (C1-INH), which plays a role in regulating the body's complement system. Involvement of the digestive tract can lead to significant abdominal pain, while swelling in the upper airways can be life-threatening, necessitating prompt medical attention.

Recognising the Signs and Symptoms

The presentation of hereditary angioedema varies among individuals. Visible swelling commonly occurs in the extremities, such as hands, feet, lips, and eyelids. Internal swelling can affect the gastrointestinal tract, manifesting as nausea, vomiting, diarrhoea, and severe abdominal pain. Swelling in the mouth, throat, or airways is less common but poses a significant risk, potentially causing difficulty swallowing, voice changes, or breathing difficulties. It is crucial to seek emergency medical assistance immediately if breathing or swallowing is compromised. Some individuals may experience a non-itchy rash, known as erythema marginatum, preceding or during an attack. HAE attacks are unpredictable, typically lasting between three to five days, and often begin in childhood or adolescence, potentially worsening after puberty.

Genetic Factors and Triggers

Hereditary angioedema is primarily caused by inherited genetic mutations. The most common types, Type I and Type II HAE, are linked to variations in the *SERPING1* gene, affecting the production or function of C1-INH. Type I HAE involves insufficient C1-INH levels, while Type II HAE involves a C1-INH protein that does not function correctly. Other genetic mutations, such as those in the *F12* gene, can lead to HAE with normal C1-INH. The condition follows an autosomal dominant inheritance pattern, meaning a single copy of the altered gene from either parent can cause the disorder. While many cases have a family history, spontaneous genetic mutations can also occur. Attacks can be triggered by various factors, including physical trauma, dental procedures, surgery, emotional stress, and viral infections, although many attacks occur without an identifiable trigger.

Diagnostic Pathways

Diagnosing hereditary angioedema involves a comprehensive approach. Healthcare professionals will conduct a physical examination and gather detailed information about the patient's symptoms and medical history, including family history of similar conditions. Specific blood tests are essential to measure C1-INH levels and assess its functional capacity. In some instances, genetic testing may be performed to identify the specific gene mutations responsible for the condition.

Management and Treatment Strategies

Management of hereditary angioedema focuses on treating acute attacks and preventing future episodes. On-demand medications, such as Berinert® or Kalbitor®, are administered at the onset of an attack to reduce its severity and duration. Prophylactic medications, including Cinryze®, Haegarda®, or Takhzyro®, are used to lower the frequency of attacks, either long-term or in anticipation of known triggers like medical procedures. It is important to note that medications commonly used for allergic reactions, such as antihistamines and epinephrine, are not effective for HAE attacks. Patients should always have access to their prescribed on-demand medication.

Synonyms and Alternative Classifications

Hereditary angioedema is known by several other clinical terms and abbreviations. These include hereditary angioneurotic oedema, familial angioedema, HAE, HANE, and C1 esterase inhibitor deficiency. It is also sometimes referred to by historical names such as Bannister disease or Quincke disease. The ICD-11 classification places hereditary angioedema under code 4A00.14, within the broader category of Diseases of the immune system, specifically Primary immunodeficiencies due to disorders of innate immunity, and more precisely under Defects in the complement system. This distinguishes it from acquired angioedema (ICD-11 code 4A00.15).

Frequently asked questions

What is the ICD-11 classification for Hereditary angioedema?
The ICD-11 classification for Hereditary angioedema is 4A00.14.
How is Hereditary angioedema defined in ICD-11?
In ICD-11, Hereditary angioedema is defined as a group of disorders characterized by recurrent episodes of angioedema, typically caused by genetically determined deficiency of C1 inhibitor.
What are the main types of Hereditary angioedema recognized in ICD-11?
ICD-11 recognizes types based on C1 inhibitor levels: Type I and Type II involve low absolute or functional levels of C1 inhibitor, respectively. Type III, a minority of cases, presents with normal C1 inhibitor levels due to mutations in genes other than SERPING1.
How does ICD-11 classify Hereditary angioedema with normal C1 inhibitor levels?
Hereditary angioedema with normal C1 inhibitor levels is classified under code 4A00.14 as Type III, which arises from mutations in genes other than SERPING1.
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