E70.41

HCC Category Mapping

What This Code Means

Histidinemia is a rare inherited metabolic disorder where the body cannot properly break down the amino acid histidine, leading to elevated levels in blood and urine.

Coding Tips

• •This is a specific diagnosis; do not use the unspecified code E70.40 if histidinemia is documented
• •Often asymptomatic but may be detected through newborn screening; document any clinical manifestations if present

Clinical Significance

Histidinemia is a rare autosomal recessive metabolic disorder caused by deficiency of histidase enzyme, leading to elevated histidine levels in blood and urine. Once considered potentially pathogenic, histidinemia is now generally regarded as a benign metabolic variant in most cases, though some studies suggest possible associations with learning disabilities or speech delays in a subset of affected individuals. No specific treatment is typically required.

Documentation Requirements

• ✓Documentation should include elevated plasma histidine levels (typically above 5 mg/dL), positive urine ferric chloride test or amino acid analysis results, enzyme activity testing if performed, and clinical assessment for any developmental or neurological abnormalities.
• ✓The provider should document whether the condition is symptomatic or an incidental finding.
• ✓Newborn screening detection should be noted if applicable.

Commonly Confused Codes