E70.49

HCC Category Mapping

What This Code Means

Other rare metabolic disorders affecting histidine processing in the body, excluding histidinemia.

Coding Tips

• •Use this code for histidine metabolism disorders that are not histidinemia or unspecified
• •Ensure documentation clearly describes the specific histidine metabolism abnormality to justify use of this code

Clinical Significance

Other disorders of histidine metabolism captures rare metabolic conditions affecting histidine processing that are distinct from classic histidinemia, such as urocanic aciduria (histidase deficiency variant) and formiminoglutamic aciduria (deficiency in formiminotransferase). These conditions may be associated with more significant clinical manifestations than benign histidinemia, including intellectual disability, anemia, and immune dysfunction.

Documentation Requirements

• ✓Documentation should specify the exact histidine metabolism disorder identified, supporting laboratory evidence (urine organic acids, enzyme assays, or genetic testing), clinical manifestations, and management plan.
• ✓The provider should clearly distinguish this from histidinemia and from unspecified histidine disorders.
• ✓Any associated developmental, hematologic, or immunologic complications should be documented.

Commonly Confused Codes