E70.49 ICD-10-CM Code: Other disorders of histidine metabolism
E70.49 is not a CMS-HCC payment code. MEAT criteria · RAF calculator · HCC Buddy coding tools
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FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Metabolic disorders (E70-E88)
E70.49
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther disorders of histidine metabolism
Other rare metabolic disorders affecting histidine processing in the body, excluding histidinemia.
Buddy Insight
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).
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
MappedHCC 23
RAF 0.194
ACA/HHS
MappedHCC 28
Varies by metal level
ESRD/PACE
MappedHCC 23
RAF 0.036
RXHCC
MappedHCC 43
RAF 0.063
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for E70.49 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for E70.49 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for E70.49 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for E70.49 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for E70.49 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for E70.49 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for E70.49 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is E70.49 an HCC code?
Yes. E70.49 maps to Other Significant Endocrine and Metabolic Disorders under the V24 model but is not retained in V28.
- Code
- E70.49
- Description
- Other disorders of histidine metabolism
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF
- —
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
Work E70.49 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for E70.49
For E70.49 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed E70.49 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
E70.49 is the ICD-10-CM diagnosis code for other disorders of histidine metabolism. Other rare metabolic disorders affecting histidine processing in the body, excluding histidinemia. E70.49 sits in the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89), within the section covering metabolic disorders (e70-e88).
Under the older CMS-HCC V24 model, E70.49 maps to Other Significant Endocrine and Metabolic Disorders (HCC 23) with a community, non-dual, aged base RAF weight of 0.194. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Use this code for histidine metabolism disorders that are not histidinemia or unspecified. Because E70.49 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for E70.49 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
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
- •E70.41 (Histidinemia) is the specific code for that condition.
- •E70.40 (Disorders of histidine metabolism, unspecified) is used when the type cannot be determined.
- •E70.89 (Other disorders of aromatic amino-acid metabolism) covers broader amino acid metabolism disorders.
- •D53.1 (Other megaloblastic anemias, not elsewhere classified) may be relevant for folate-related histidine metabolism disorders.