What is ICD-10 code E78.79?

E78.79 is the ICD-10-CM diagnosis code for Other disorders of bile acid and cholesterol metabolism. Other rare disorders affecting how the body processes bile acids and cholesterol that are not classified elsewhere. It belongs to the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89). E78.79 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. E78.79 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. E78.79 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. E78.79 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.

What is the V28 vs V24 difference for E78.79?

E78.79 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither community model rewards E78.79 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's V28/V24 community RAF score in either version. It does, however, map under the Part D RxHCC model (Disorders of Fatty-Acid and Lipid Metabolism), which affects the ESRD and/or Part D (RxHCC) risk scores. Coders should check whether provider documentation supports a more specific child code that does map to a community payment HCC.

What should coders know when reporting E78.79?

Use this code for documented bile acid or cholesterol metabolism disorders not specified by E78.71 or E78.72 Include specific diagnosis name and relevant lab values in the medical record for clarity

2026 ICD-10-CM E78.79: Other disorders of bile acid

ICD-10-CM Code View

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Code lookupE78.79Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

E78.79

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

Other disorders of bile acid and cholesterol metabolism

Other rare disorders affecting how the body processes bile acids and cholesterol that are not classified elsewhere.

Buddy Insight

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

N/A

—

Not risk-adjusted for this model/period.

Not mapped

RXHCC

Mapped

HCC 47

Disorders of Fatty-Acid and L...

Not separately weighted

Code Book Path

Official

E78Disorders of lipoprotein metabolism and other lipidemias

E78.7Disorders of bile acid and cholesterol metabolism

E78.79Other disorders of bile acid and cholesterol metabolism

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for E78.79 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for E78.79 in this effective period.

Related Child Codes

Official

E78.70Disorder of bile acid and cholesterol metabolism, unspecified

E78.71Barth syndrome

E78.72Smith-Lemli-Opitz syndrome

Includes

Official

ICD-10-CM does not list Includes notes for E78.79 in this effective period.

Excludes 1

Official

Niemann-Pick disease type C (E75.242)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for E78.79 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for E78.79 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for E78.79 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Specific bile acid or cholesterol metabolism disorder documented (e.g., cerebrotendinous xanthomatosis, specific bile acid synthesis defect)

Confirmatory diagnostic testing: serum cholestanol levels (for CTX), urine bile acid profile, genetic testing

Clinical manifestations specific to the identified disorder

Treatment plan: chenodeoxycholic acid or cholic acid replacement therapy

MEAT Support

HCC Buddy guidance

Specific bile acid or cholesterol metabolism disorder documented (e.g., cerebrotendinous xanthomatosis, specific bile acid synthesis defect)

Confirmatory diagnostic testing: serum cholestanol levels (for CTX), urine bile acid profile, genetic testing

Clinical manifestations specific to the identified disorder

Treatment plan: chenodeoxycholic acid or cholic acid replacement therapy

Audit Caution

HCC Buddy guidance

Not recognizing cerebrotendinous xanthomatosis (CTX) as a treatable bile acid synthesis disorder coded here

Using unspecified E78.70 when a named bile acid synthesis defect is documented

Coding only the neurological manifestations of CTX (neuropathy, ataxia) without the underlying metabolic diagnosis

Confusing bile acid synthesis defects with cholestatic liver diseases of other etiologies

Common Mistakes

HCC Buddy guidance

E78.70 — Disorder of bile acid and cholesterol metabolism, unspecified: use only when the specific disorder is unknown

E75.5 — Other lipid storage disorders: for intracellular lipid accumulation, not bile acid pathway defects

E78.2 — Mixed hyperlipidemia: circulating lipid elevation, not bile acid synthesis defect

G60.9 — Hereditary and idiopathic neuropathy, unspecified: CTX may present with neuropathy, but code the metabolic cause

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 E78.79 an HCC code?

E78.79 is not in the CMS-HCC V28 or V24 community payment model, but it does map to Disorders of Fatty-Acid and Lipid Metabolism under the Part D RxHCC model.

Code: E78.79
Description: Other disorders of bile acid and cholesterol metabolism
HCC (V28): No CMS-HCC V28 mapping
RAF: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

RxHCCHCC 47, Disorders of Fatty-Acid and Lipid Metabolism

Not separately weighted

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 E78.79 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for E78.79

For E78.79to 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 E78.79 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

E78.79 is the ICD-10-CM diagnosis code for other disorders of bile acid and cholesterol metabolism. Other rare disorders affecting how the body processes bile acids and cholesterol that are not classified elsewhere. E78.79 sits in the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89), within the section covering metabolic disorders (e70-e88).

E78.79 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

This code does not map to a CMS-HCC V28 payment category. Capture depends on documentation that supports the diagnosis; verify the HCC assignment against the current CMS mapping for the applicable payment year. Coders reviewing E78.79 should check whether additional documentation would support a more specific child code in the same hierarchy that does map to a payment HCC, capturing the correct specificity is the highest-impact RAF improvement available within accurate coding.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for E78.79 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use this code for documented bile acid or cholesterol metabolism disorders not specified by E78.71 or E78.72
•Include specific diagnosis name and relevant lab values in the medical record for clarity

Clinical Significance

Other disorders of bile acid and cholesterol metabolism captures specific bile acid synthesis defects such as cerebrotendinous xanthomatosis (CTX), 3-beta-hydroxy-delta-5-C27-steroid oxidoreductase deficiency, and other inborn errors of bile acid synthesis. These conditions can be treatable with chenodeoxycholic acid replacement, making accurate diagnosis critically important.

Documentation Requirements

✓Specific bile acid or cholesterol metabolism disorder documented (e.g., cerebrotendinous xanthomatosis, specific bile acid synthesis defect)
✓Confirmatory diagnostic testing: serum cholestanol levels (for CTX), urine bile acid profile, genetic testing
✓Clinical manifestations specific to the identified disorder
✓Treatment plan: chenodeoxycholic acid or cholic acid replacement therapy
✓Provider statement confirming this is a metabolic disorder of bile acid/cholesterol pathway

Commonly Confused Codes

•E78.70: Disorder of bile acid and cholesterol metabolism, unspecified: use only when the specific disorder is unknown
•E75.5: Other lipid storage disorders: for intracellular lipid accumulation, not bile acid pathway defects
•E78.2: Mixed hyperlipidemia: circulating lipid elevation, not bile acid synthesis defect
•G60.9: Hereditary and idiopathic neuropathy, unspecified: CTX may present with neuropathy, but code the metabolic cause