ICD-11 Codes
for 4A00.13 - Immunodeficiency with factor D anomaly

Teodor Jurukovski January 1, 1970

Fact checked by: Teodor Jurukovski

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Understanding Immunodeficiency with Factor D Anomaly

Immunodeficiency with factor D anomaly, identified by ICD-11 code 4A00.13, is a rare primary immunodeficiency disorder. It stems from a deficiency or anomaly in Factor D, a crucial protein within the complement system's alternative pathway. The complement system is vital for innate immunity, aiding in the defence against infections and the clearance of cellular debris. A deficiency in Factor D impairs the proper functioning of this pathway, leading to an increased susceptibility to certain types of bacterial infections. This condition is a specific type of complement deficiency, impacting the body's ability to effectively combat pathogens.

Clinical Manifestations of Factor D Deficiency

Individuals with immunodeficiency with factor D anomaly often experience recurrent and potentially severe bacterial infections. The most commonly identified pathogens are encapsulated bacteria, particularly species of Neisseria, which can lead to serious conditions such as meningitis and sepsis. Infections caused by Haemophilus influenzae and Streptococcus pneumoniae are also frequently observed. While some individuals may remain asymptomatic for extended periods, the onset of a severe infection can be the first indication of the underlying deficiency. The increased susceptibility to these infections is a hallmark presentation of Factor D deficiency.

Genetic Basis and Causes

Immunodeficiency with factor D anomaly is primarily a genetic disorder, typically inherited. It arises from mutations in the Complement Factor D (CFD) gene. These genetic alterations lead to either a complete absence or a significant reduction in the functional levels of Factor D protein. The deficiency is often passed down through families, with reported cases involving homozygous or compound heterozygous variants in the CFD gene. While rare, understanding the genetic basis is key to identifying affected individuals and their family members.

Diagnostic Approaches for Factor D Deficiency

Diagnosing immunodeficiency with factor D anomaly involves a combination of clinical assessment and laboratory testing. A history of recurrent, severe bacterial infections, especially those caused by Neisseria species, raises clinical suspicion. Laboratory investigations typically include functional complement assays, such as the AP50 test, which will show undetectable activity in individuals with complete Factor D deficiency. Specific measurement of Factor D protein levels, often using ELISA, confirms the deficiency. Genetic testing of the CFD gene can further validate the diagnosis by identifying specific mutations.

Management and Prevention Strategies

The management of immunodeficiency with factor D anomaly focuses on preventing and treating infections. Key strategies include comprehensive immunization schedules, particularly against encapsulated bacteria like Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae. Prompt and appropriate antibiotic treatment is crucial for any suspected or confirmed infection. In some cases, prophylactic antibiotic therapy may be considered to reduce the frequency of infections. While specific replacement therapies for Factor D are not standard, managing the underlying susceptibility through vaccination and timely medical intervention is paramount.

Coding and Documentation for ICD-11 Code 4A00.13

For accurate medical billing and record-keeping, the ICD-11 code 4A00.13 is used to classify 'Immunodeficiency with factor D anomaly'. This code falls under the broader category of primary immunodeficiencies and specifically denotes a defect in complement factor D. Common clinical synonyms include 'Factor D deficiency' and 'Complement factor D deficiency'. Precise documentation of the patient's history of recurrent infections, diagnostic test results (such as low AP50 activity or undetectable Factor D levels), and any genetic findings is essential for appropriate coding and clinical management. This specific ICD-11 code is reportable and billable when a diagnosis of Factor D anomaly is confirmed.