E72.21 ICD-10-CM Code: Argininemia
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FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Metabolic disorders (E70-E88)
E72.21
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceArgininemia
Argininemia is a rare genetic disorder where the body cannot properly break down the amino acid arginine, causing it to build up to harmful levels in the blood and urine. This buildup can lead to neurological problems, developmental delays, and other serious health complications.
Buddy Insight
Argininemia (arginase deficiency) is a urea cycle disorder where deficiency of the enzyme arginase causes accumulation of arginine in blood and cerebrospinal fluid.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
MappedHCC 23
RAF 0.194
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 23
RAF 0.0
RXHCC
MappedHCC 43
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for E72.21 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for E72.21 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for E72.21 in this effective period.
Excludes 1
Official- disorders of ornithine metabolism (E72.4)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for E72.21 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for E72.21 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for E72.21 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is E72.21 an HCC code?
Yes. E72.21 maps to Other Significant Endocrine and Metabolic Disorders under the V24 model but is not retained in V28.
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. 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 E72.21 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for E72.21
For E72.21to 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 E72.21 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
E72.21 is the ICD-10-CM diagnosis code for argininemia. Argininemia is a rare genetic disorder where the body cannot properly break down the amino acid arginine, causing it to build up to harmful levels in the blood and urine. This buildup can lead to neurological problems, developmental delays, and other serious health complications. E72.21 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, E72.21 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.
Argininemia is a metabolic disorder requiring documentation of the specific type and any associated complications (such as hyperammonemia, seizures, or developmental delay) for complete coding. Because E72.21 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 E72.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Argininemia is a metabolic disorder requiring documentation of the specific type and any associated complications (such as hyperammonemia, seizures, or developmental delay) for complete coding
- •This condition is typically lifelong and should be coded as a principal diagnosis when it is the primary reason for the encounter; look for related codes for complications or management of the condition
Clinical Significance
Argininemia (arginase deficiency) is a urea cycle disorder where deficiency of the enzyme arginase causes accumulation of arginine in blood and cerebrospinal fluid. Unlike other urea cycle disorders, argininemia typically presents insidiously in childhood (age 2-4) with progressive spastic diplegia, seizures, and intellectual decline rather than acute hyperammonemic crises. Hyperammonemia when it occurs is usually milder than in other urea cycle disorders.
Documentation Requirements
- ✓Document elevated plasma arginine levels, arginase enzyme activity, genetic testing for ARG1 mutations, neurological assessment including spasticity evaluation, developmental milestones, ammonia levels, and treatment regimen (low-protein diet with essential amino acid supplementation, nitrogen scavenger therapy if needed).
- ✓Record spasticity management plan.
Commonly Confused Codes
- •E72.22 (Arginosuccinic aciduria) which involves a different urea cycle enzyme
- •E72.23 (Citrullinemia) for argininosuccinate synthetase deficiency
- •E72.20 (Disorder of urea cycle metabolism, unspecified) which lacks specificity
- •G80.1 (Spastic diplegic cerebral palsy) when the metabolic basis is missed.