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ICD Hub / Diseases of the immune system (D80–D89) / 4A00.15 - Acquired angioedema
ICD-11

ICD-11 Codes
for 4A00.15 - Acquired angioedema
Teodor Jurukovski January 1, 1970
Fact checked by: Teodor Jurukovski
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Understanding Acquired Angioedema (ICD-11 Code 4A00.15)

Acquired angioedema, identified by the ICD-11 code 4A00.15, is a rare condition characterised by recurrent episodes of swelling. This condition arises from an acquired deficiency or inactivation of the C1 inhibitor (C1-INH) protein. Clinically, it closely resembles hereditary angioedema but is not inherited. Acquired angioedema is distinct from conditions associated with urticaria. It can manifest as Type I, linked to lymphoproliferative disorders, or Type II, resulting from autoantibodies targeting C1 inhibitor.

Recognising the Signs of Acquired Angioedema

Patients experiencing acquired angioedema typically present with well-demarcated, non-pitting edema affecting deep subcutaneous and submucosal tissues. Swelling commonly occurs on the face, lips, tongue, limbs, and genitals. Internal involvement can lead to severe abdominal pain due to gastrointestinal mucosa edema. A critical concern is the potential for upper airway edema, which can be life-threatening and necessitate urgent medical intervention. Unlike some allergic reactions, acquired angioedema is not typically accompanied by urticaria. Episodes can last for several days and their frequency is unpredictable.

What Causes Acquired Angioedema?

The primary cause of acquired angioedema (AAE) is an acquired deficiency of C1 inhibitor (C1-INH). This deficiency can occur through two main mechanisms: consumption of C1-INH (Type I AAE) or inactivation of C1-INH by autoantibodies (Type II AAE). Type I AAE is often associated with underlying conditions such as lymphoproliferative disorders or autoimmune diseases. Type II AAE involves the development of autoantibodies specifically directed against C1-INH. AAE typically affects adults, often presenting after the age of 40, and is not associated with a family history of angioedema.

Diagnosing Acquired Angioedema

The diagnosis of acquired angioedema (AAE) relies on a combination of clinical presentation and specific laboratory tests. Key diagnostic indicators include low levels of C1 inhibitor activity and low levels of complement factors C3 and C4. The presence of autoantibodies against C1-INH is also a significant finding, particularly in Type II AAE. While clinical symptoms of recurrent swelling are crucial, laboratory confirmation is essential to differentiate AAE from other forms of angioedema and to guide appropriate management.

Managing Acquired Angioedema

Treatment for acquired angioedema (AAE) often requires a specialised approach, as standard treatments for allergic angioedema, such as antihistamines, corticosteroids, and epinephrine, may be less effective. Management strategies focus on addressing the underlying C1-INH deficiency. This can involve the administration of plasma-derived or recombinant C1-INH concentrate to manage acute attacks. Medications like icatibant (a bradykinin B2 receptor antagonist) or ecallantide (a bradykinin pathway inhibitor) may also be used. In some cases, treating the underlying autoimmune or lymphoproliferative disorder can lead to improvement in AAE symptoms.

Coding and Documenting Acquired Angioedema

For accurate medical billing and record-keeping, the ICD-11 code for Acquired angioedema is **4A00.15**. This code is used to report the specific diagnosis of acquired angioedema. Common clinical synonyms that may appear in patient documentation include Acquired angioneurotic oedema, AAE, Acquired angioedema type I, Acquired angioedema type II, and Acquired C1 Inhibitor Deficiency. When documenting, healthcare providers should clearly indicate the presence of swelling or edema and any associated symptoms, ensuring that the diagnosis aligns with the ICD-11 classification for proper reporting and reimbursement. This ICD-11 code for Acquired angioedema is reportable and billable.

Frequently asked questions

What is the ICD-11 classification for Acquired Angioedema (4A00.15)?
Acquired angioedema (4A00.15) is classified under ICD-11 within Diseases of the immune system, specifically under Primary immunodeficiencies due to disorders of innate immunity, and further categorized as Defects in the complement system. It is characterized by an acquired deficiency of C1 inhibitor.
How is Acquired Angioedema (4A00.15) defined in ICD-11?
In ICD-11, Acquired Angioedema (4A00.15) is defined as a condition that is clinically similar to hereditary angioedema, is not associated with urticaria, and results from an acquired deficiency of C1 inhibitor.
What are the types of Acquired Angioedema (4A00.15) recognized in ICD-11?
ICD-11 recognizes two types of acquired angioedema: Type I, which may be associated with a lymphoproliferative disorder, and Type II, which is an isolated phenomenon due to an autoantibody directed against C1 inhibitor.
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