E88.49
BillableOther mitochondrial metabolism disorders
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is E88.49 an HCC code?
Yes. E88.49 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 E88.49
For E88.49to 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 E88.49 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
E88.49 is the ICD-10-CM diagnosis code for other mitochondrial metabolism disorders. Other rare mitochondrial metabolism disorders not classified elsewhere, affecting how cells produce and use energy. E88.49 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, E88.49 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 mitochondrial disorders that don't fit into the more specific categories (E88.40-E88.43). Because E88.49 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 E88.49 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
This code captures named mitochondrial metabolism disorders that do not have their own specific code, such as Leigh syndrome, Kearns-Sayre syndrome, NARP (Neuropathy, Ataxia, and Retinitis Pigmentosa), and other complex mitochondrial disorders. Accurate identification supports appropriate subspecialty management.
Documentation Requirements
- ✓Specific named mitochondrial disorder documented (Leigh syndrome, Kearns-Sayre, NARP, etc.)
- ✓Genetic testing or clinical diagnostic criteria met
- ✓Affected organ systems and severity assessment
- ✓Multi-system evaluation results
- ✓Current treatment and support measures
- ✓Documentation that the condition is NOT MELAS (E88.41), MERRF (E88.42), or tRNA synthetase disorder (E88.43)
Commonly Confused Codes
- •E88.41 — MELAS syndrome: has its own specific code; do not use E88.49
- •E88.42 — MERRF syndrome: has its own specific code; do not use E88.49
- •E88.43 — Disorders of mitochondrial tRNA synthetases: has its own specific code
- •E88.40 — Mitochondrial metabolism disorder, unspecified: use only when the specific type is unknown
- •G71.3 — Mitochondrial myopathy: when myopathy is the sole manifestation