E70.40

HCC Category Mapping

What This Code Means

A metabolic disorder affecting the breakdown of histidine (an amino acid) when the specific type is not identified.

Coding Tips

• •This is an unspecified code; use only when the specific histidine metabolism disorder cannot be determined
• •Query documentation to determine if histidinemia or other specified disorder of histidine metabolism is present

Clinical Significance

Unspecified disorder of histidine metabolism indicates an identified abnormality in how the body processes the amino acid histidine, but the specific condition has not been determined. Histidine metabolism disorders are generally benign, with histidinemia being the most common and typically asymptomatic, but some variants may be associated with intellectual disability or speech delays, making accurate diagnosis important for prognostic counseling.

Documentation Requirements

• ✓Documentation should include elevated histidine levels on amino acid analysis, any clinical manifestations present, newborn screening results if applicable, and the plan for further diagnostic evaluation.
• ✓The provider should document why the specific disorder cannot be determined and note any developmental assessments performed.
• ✓Family history of metabolic disorders should be recorded.

Commonly Confused Codes