ICD-11 Codes
for 4A00.1Y - Other specified defects in the complement system

Teodor Jurukovski January 1, 1970

Fact checked by: Teodor Jurukovski

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Understanding Other Specified Defects in the Complement System

The ICD-11 code 4A00.1Y represents 'Other specified defects in the complement system'. This classification falls under primary immunodeficiencies, indicating inherited conditions where specific components of the body's complement system, a crucial part of the immune defence, are not functioning correctly. These defects can lead to a range of health issues, primarily related to increased susceptibility to infections and the development of autoimmune conditions.

Recognizing the Signs: Symptoms of Complement System Defects

Individuals with other specified defects in the complement system may experience a variety of symptoms, often related to impaired immune responses. Common clinical presentations include:

• Increased susceptibility to recurrent and severe infections, particularly those caused by bacteria such as Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae.
• Development of autoimmune diseases, including Systemic Lupus Erythematosus (SLE), nephritis, joint inflammation, and vasculitis.
• Renal diseases.
• Episodes of angioedema, characterized by swelling under the skin or within the gastrointestinal tract.
• Specific infections like recurrent Neisseria infections, which can lead to meningitis.

In some rare instances, specific genetic defects within the complement system pathways may be associated with developmental abnormalities.

What Causes Complement System Deficiencies?

The primary cause of conditions classified under ICD-11 code 4A00.1Y is inherited genetic defects. These are considered primary immunodeficiencies, meaning they are congenital and result from mutations in the genes responsible for producing complement proteins or their regulatory molecules. These inherited deficiencies impair the normal function of the complement cascade, a vital part of the innate immune system.

Diagnosing Other Specified Defects in the Complement System

The diagnosis of other specified defects in the complement system typically involves a combination of clinical evaluation and laboratory testing. Healthcare professionals will assess the patient's medical history, looking for patterns of recurrent infections or autoimmune symptoms. Diagnostic procedures often include:

• Laboratory serum analysis to measure the levels and function of specific complement proteins (e.g., C3, C4, Factor H, Factor I, C1 inhibitor, Mannan-binding lectin).
• Genetic testing may be employed to identify specific gene mutations responsible for the complement deficiency.

Accurate diagnosis is essential to guide appropriate management strategies.

Managing Complement System Defects

Treatment and management for individuals with other specified defects in the complement system focus on preventing and treating infections, managing autoimmune manifestations, and addressing specific complications. Key management considerations include:

• Prophylactic and therapeutic use of antibiotics to prevent and treat bacterial infections.
• Administering appropriate immunizations to protect against common pathogens.
• Specific therapies may be required for associated conditions such as Hereditary Angioedema (HAE) or atypical hemolytic uremic syndrome (aHUS).
• Management of autoimmune diseases like SLE.

It is important to note that for certain deficiencies, such as Mannan-binding lectin (MBL) deficiency, immunoglobulin replacement therapy is not indicated.

Alternative Names for Complement System Defects

The ICD-11 code 4A00.1Y encompasses a range of specific complement system defects, each with its own clinical synonyms and patient-friendly terms. These include conditions such as Complement component C3 deficiency, Recurrent Neisseria infections due to factor D deficiency, Immunodeficiency with CD46 deficiency (also known as Membrane cofactor protein deficiency), Immunodeficiency with decay accelerating factor deficiency (also known as Immunodeficiency with CD55 deficiency), CHAPLE syndrome, Immunodeficiency with factor H anomaly, Immunodeficiency with factor I anomaly, Immunodeficiency with properdin deficiency, Immunodeficiency with CD59 deficiency, Immunodeficiency with MASP-2 deficiency, Mannan-binding lectin deficiency (also known as Mannose-binding protein deficiency), Immunodeficiency with ficolin-3 deficiency, and Angioedema due to disordered complement activation or kinin metabolism. These terms help describe the specific nature of the complement system issue.

Coding and Documentation for 4A00.1Y

The ICD-11 code 4A00.1Y, 'Other specified defects in the complement system', is a billable and reportable code used in healthcare settings. Proper documentation is crucial for accurate medical coding and billing. Clinicians should ensure that patient records clearly specify the nature of the complement defect, whether it is a deficiency in a particular component (e.g., C3, Factor H) or a related anomaly. This detailed documentation supports the correct application of the 4A00.1Y code and any associated condition codes, facilitating appropriate reimbursement and tracking of patient care.