What is ICD-10 code E72.4?

E72.4 is the ICD-10-CM diagnosis code for Disorders of ornithine metabolism. It belongs to the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89). E72.4 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. E72.4 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. E72.4 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. E72.4 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does E72.4 map to under V28?

E72.4 does not map to a CMS-HCC V28 payment category. Check the current CMS-HCC V28 model file for payment year 2026 rather than an older V24 tip sheet.

What does E72.4 pay in RAF?

E72.4 has no separately stated V28 community RAF weight. If it is not a V28 payment HCC, it adds nothing to a community RAF score.

What is the V28 vs V24 difference for E72.4?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. E72.4 was a payment HCC under V24 (Other Significant Endocrine and Metabolic Disorders) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What documentation supports E72.4?

Verify the specific type of ornithine metabolism disorder (such as gyrate atrophy) as this code may require additional specificity depending on documentation and payer requirements Look for associated conditions like progressive vision loss or retinal degeneration, as these complications should be coded separately if documented Because E72.4 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score. See the MEAT criteria checklist at /meat-criteria for what Monitor, Evaluate, Assess, or Treat looks like in a note. MEAT is generic documentation evidence, not a payer-specific rule.

2026 ICD-10-CM E72.4: Disorders of ornithine

E72.4 is not a CMS-HCC payment code. MEAT criteria · RAF calculator · free HCC coding tools

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Code lookupE72.4Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Metabolic disorders (E70-E88)

E72.4

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Disorders of ornithine metabolism

This is a rare metabolic disorder where the body cannot properly process ornithine, an amino acid needed for normal protein metabolism and liver function. This can lead to vision problems, muscle weakness, and other complications if not managed.

Buddy Insight

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Mapped

HCC 23

Other Significant Endocrine a...

RAF 0.194

ACA/HHS

Mapped

HCC 28

HHS-HCC 28

Varies by metal level

ESRD/PACE

Mapped

HCC 23

Other Significant Endocrine a...

RAF 0.036

RXHCC

Mapped

HCC 43

Other Significant Endocrine a...

RAF 0.063

Code Book Path

Official

E72Other disorders of amino-acid metabolism

E72.4Disorders of ornithine metabolism

Inclusion Terms

Official

Hyperammonemia-Hyperornithinemia-Homocitrullinemia syndrome
Ornithinemia (types I, II)
Ornithine transcarbamylase deficiency

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for E72.4 in this effective period.

Related Child Codes

Official

E72.0Disorders of amino-acid transport

E72.1Disorders of sulfur-bearing amino-acid metabolism

E72.2Disorders of urea cycle metabolism

E72.3Disorders of lysine and hydroxylysine metabolism

E72.5Disorders of glycine metabolism

Includes

Official

ICD-10-CM does not list Includes notes for E72.4 in this effective period.

Excludes 1

Official

hereditary choroidal dystrophy (H31.2-)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for E72.4 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for E72.4 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for E72.4 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Specific ornithine metabolism disorder identified (e.g., gyrate atrophy, hyperornithinemia-hyperammonemia-homocitrullinuria syndrome)

Laboratory findings including plasma ornithine levels and relevant enzyme assays

Genetic testing confirmation if performed

Documentation of ophthalmological findings if gyrate atrophy is present

MEAT Support

HCC Buddy guidance

Specific ornithine metabolism disorder identified (e.g., gyrate atrophy, hyperornithinemia-hyperammonemia-homocitrullinuria syndrome)

Laboratory findings including plasma ornithine levels and relevant enzyme assays

Genetic testing confirmation if performed

Documentation of ophthalmological findings if gyrate atrophy is present

Audit Caution

HCC Buddy guidance

Confusing ornithine metabolism disorders with urea cycle defects — while ornithine participates in the urea cycle, E72.4 captures primary ornithine metabolism abnormalities

Failing to code the retinal findings of gyrate atrophy separately when documented

Missing hyperammonemia as a complication that should be coded additionally

Using the unspecified amino acid code E72.9 when E72.4 is the appropriate specific code

Common Mistakes

HCC Buddy guidance

E72.29 — Other disorders of urea cycle metabolism: ornithine is involved in the urea cycle but E72.4 is specific to ornithine metabolism defects

E72.89 — Other specified disorders of amino-acid metabolism: a broader residual code

E72.20 — Disorder of urea cycle metabolism, unspecified: non-specific urea cycle code

H31.20-H31.29 — Hereditary choroidal dystrophy: if gyrate atrophy is present, code both the metabolic and the retinal condition

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 E72.4 an HCC code?

Yes. E72.4 maps to Other Significant Endocrine and Metabolic Disorders under the V24 model but is not retained in V28.

Code: E72.4
Description: Disorders of ornithine metabolism
HCC (V28): No CMS-HCC V28 mapping
RAF: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

V24HCC 23, Other Significant Endocrine and Metabolic Disorders

0.194

ESRDHCC 23, Other Significant Endocrine and Metabolic Disorders

0.036

RxHCCHCC 43, Other Significant Endocrine and Metabolic Disorders

0.063

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 E72.4 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for E72.4

For E72.4 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 E72.4 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

E72.4 is the ICD-10-CM diagnosis code for disorders of ornithine metabolism. This is a rare metabolic disorder where the body cannot properly process ornithine, an amino acid needed for normal protein metabolism and liver function. This can lead to vision problems, muscle weakness, and other complications if not managed. E72.4 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, E72.4 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.

Verify the specific type of ornithine metabolism disorder (such as gyrate atrophy) as this code may require additional specificity depending on documentation and payer requirements. Because E72.4 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 E72.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Verify the specific type of ornithine metabolism disorder (such as gyrate atrophy) as this code may require additional specificity depending on documentation and payer requirements
•Look for associated conditions like progressive vision loss or retinal degeneration, as these complications should be coded separately if documented

Clinical Significance

Disorders of ornithine metabolism, such as gyrate atrophy of the choroid and retina and hyperornithinemia-hyperammonemia-homocitrullinuria syndrome, cause progressive vision loss and potentially life-threatening hyperammonemia. These rare genetic conditions require specialized metabolic care, dietary management, and routine ophthalmological monitoring. Risk adjustment capture is important due to the high resource utilization and complex care needs.

Documentation Requirements

✓Specific ornithine metabolism disorder identified (e.g., gyrate atrophy, hyperornithinemia-hyperammonemia-homocitrullinuria syndrome)
✓Laboratory findings including plasma ornithine levels and relevant enzyme assays
✓Genetic testing confirmation if performed
✓Documentation of ophthalmological findings if gyrate atrophy is present
✓Current treatment plan including dietary protein or arginine restriction

Excludes 1, Do NOT code together

hereditary choroidal dystrophy (H31.2-)

Commonly Confused Codes

•E72.29: Other disorders of urea cycle metabolism: ornithine is involved in the urea cycle but E72.4 is specific to ornithine metabolism defects
•E72.89: Other specified disorders of amino-acid metabolism: a broader residual code
•E72.20: Disorder of urea cycle metabolism, unspecified: non-specific urea cycle code
•H31.20-H31.29: Hereditary choroidal dystrophy: if gyrate atrophy is present, code both the metabolic and the retinal condition