E71.120 ICD-10-CM Code: Methylmalonic acidemia
HCC Buddy Code Card
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FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Metabolic disorders (E70-E88)
E71.120
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMethylmalonic acidemia
A rare inherited metabolic disorder where the body cannot properly convert methylmalonic acid, leading to its accumulation and potential neurological and blood-related complications.
Buddy Insight
Methylmalonic acidemia is a serious inherited metabolic disorder caused by deficiency of methylmalonyl-CoA mutase, leading to accumulation of methylmalonic acid with potential for life-threatening metabolic crises.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
MappedHCC 23
RAF 0.230
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 E71.120 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for E71.120 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for E71.120 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for E71.120 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for E71.120 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for E71.120 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for E71.120 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 E71.120 an HCC code?
Yes. E71.120 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.
MEAT Criteria for E71.120
For E71.120to 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 E71.120 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
E71.120 is the ICD-10-CM diagnosis code for methylmalonic acidemia. A rare inherited metabolic disorder where the body cannot properly convert methylmalonic acid, leading to its accumulation and potential neurological and blood-related complications. E71.120 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, E71.120 maps to Other Significant Endocrine and Metabolic Disorders (HCC 23) with a community, non-dual, aged base RAF weight of 0.230. 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.
Distinguish between methylmalonic acidemia (E71.120) and other forms of methylmalonic aciduria. Because E71.120 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 E71.120 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Distinguish between methylmalonic acidemia (E71.120) and other forms of methylmalonic aciduria
- •Document whether this is vitamin B12-responsive or non-responsive if documented in the medical record
Clinical Significance
Methylmalonic acidemia is a serious inherited metabolic disorder caused by deficiency of methylmalonyl-CoA mutase, leading to accumulation of methylmalonic acid with potential for life-threatening metabolic crises. Patients face risks of renal failure, pancreatitis, and neurological damage including movement disorders and developmental delays. Some forms respond to vitamin B12 supplementation, making accurate diagnosis critical for treatment planning.
Documentation Requirements
- ✓Document whether the condition is vitamin B12-responsive or non-responsive, plasma methylmalonic acid and homocysteine levels, genetic mutation if known, renal function status, and history of metabolic decompensation episodes.
- ✓Record dietary protein restriction details and supplementation regimen.
Commonly Confused Codes
- •E71.121 (Propionic acidemia) which involves a different but related metabolic pathway
- •E71.128 (Other disorders of propionate metabolism) for unspecified propionate pathway defects
- •E72.12 (Methylenetetrahydrofolate reductase deficiency) which also affects methylation pathways but is a different disorder.