Adenosine deaminase deficiency, unspecified

This code signifies an inherited metabolic disorder characterized by a deficiency in the enzyme adenosine deaminase (ADA), leading to the accumulation of toxic metabolites in lymphocytes. This enzyme defect primarily impairs the development and function of both T and B lymphocytes, resulting in severe combined immunodeficiency (SCID). The "unspecified" nature indicates that the specific genetic mutation or clinical subtype of ADA deficiency is not documented.

Use this code when documentation confirms a diagnosis of adenosine deaminase deficiency but lacks further specificity regarding the genetic variant or clinical presentation. This code is appropriate for initial diagnoses where further genetic testing or detailed clinical characterization is pending or not yet available. It should be supported by clinical findings consistent with SCID and laboratory evidence of ADA deficiency.

• Avoid using this code if a more specific type of ADA deficiency (e.g., with specific genetic mutation or clinical subtype) is documented; look for more precise codes within the D81.3 category.
• Ensure documentation clearly states "adenosine deaminase deficiency" to support this code.
• Consider sequencing this code as the primary diagnosis when it is the reason for the encounter, especially in the context of initial diagnosis or management of the underlying immunodeficiency.