What is ICD-10 code E74.03?

E74.03 is the ICD-10-CM diagnosis code for Cori disease. A rare inherited metabolic disorder where the body cannot properly process glycogen due to debranching enzyme deficiency, causing muscle weakness and liver problems. It belongs to the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89). E74.03 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. E74.03 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. E74.03 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. E74.03 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 E74.03?

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. For E74.03, V28 maps to Amyloidosis, Porphyria, and Other Specified Metabolic Disorders at RAF 0.648 while V24 mapped to Other Significant Endocrine and Metabolic Disorders at RAF 0.194. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting E74.03?

Also known as Forbes disease; document presence of hepatomegaly and muscle symptoms This condition typically has a better prognosis than other glycogen storage diseases Because E74.03 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.

2026 ICD-10-CM E74.03: Cori disease

ICD-10-CM Code View

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Code lookupE74.03Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

E74.03

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

Cori disease

A rare inherited metabolic disorder where the body cannot properly process glycogen due to debranching enzyme deficiency, causing muscle weakness and liver problems.

Buddy Insight

Cori disease (Glycogen Storage Disease Type III), also known as Forbes disease, is caused by glycogen debranching enzyme deficiency.

CMS-HCC V28

Mapped

HCC 50

Amyloidosis, Porphyria, and O...

RAF 0.648

CMS-HCC V24

Mapped

HCC 23

Other Significant Endocrine a...

RAF 0.194

ACA/HHS

Mapped

HCC 27

HHS-HCC 27

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

E74Other disorders of carbohydrate metabolism

E74.0Glycogen storage disease

E74.03Cori disease

Inclusion Terms

Official

Forbes disease
Type III glycogen storage disease

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for E74.03 in this effective period.

Related Child Codes

Official

E74.00Glycogen storage disease, unspecified

E74.01von Gierke disease

E74.02Pompe disease

E74.04McArdle disease

E74.05Lysosome-associated membrane protein 2 [LAMP2] deficiency

Includes

Official

ICD-10-CM does not list Includes notes for E74.03 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for E74.03 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for E74.03 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for E74.03 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for E74.03 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Confirmed diagnosis of Cori disease, Forbes disease, or GSD Type III

Enzyme assay or genetic testing confirming debranching enzyme deficiency

Subtype specification if documented (IIIa — liver and muscle; IIIb — liver only)

Physical exam findings including hepatomegaly and muscle weakness assessment

MEAT Support

HCC Buddy guidance

Confirmed diagnosis of Cori disease, Forbes disease, or GSD Type III

Enzyme assay or genetic testing confirming debranching enzyme deficiency

Subtype specification if documented (IIIa — liver and muscle; IIIb — liver only)

Physical exam findings including hepatomegaly and muscle weakness assessment

Audit Caution

HCC Buddy guidance

Confusing Cori disease (Type III) with von Gierke disease (Type I) — both cause hepatomegaly but have different enzyme deficiencies

Not specifying the subtype (IIIa vs IIIb) in documentation when available

Coding only the liver disease or myopathy without identifying the underlying GSD

Missing late-onset cardiac complications that develop in adult patients with GSD III

Common Mistakes

HCC Buddy guidance

E74.01 — von Gierke disease (Type I): also causes hepatomegaly and hypoglycemia but involves different enzyme

E74.00 — Glycogen storage disease, unspecified: do not use when Cori disease is confirmed

E74.04 — McArdle disease (Type V): pure muscle GSD without liver involvement

E74.09 — Other glycogen storage disease: for GSD types without individual codes

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 E74.03 an HCC code?

Yes. E74.03 (Cori disease) maps to Amyloidosis, Porphyria, and Other Specified Metabolic Disorders under the CMS-HCC V28 risk adjustment model (and Other Significant Endocrine and Metabolic Disorders under V24), with a community non-dual aged RAF of 0.648. It is billable for payment year 2026.

Coder answer: E74.03 is billable and maps to V28 HCC 50, Amyloidosis, Porphyria, and Other Specified Metabolic Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: E74.03
Description: Cori disease
HCC (V28): HCC 50 — Amyloidosis, Porphyria, and Other Specified Metabolic Disorders
RAF: 0.648
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 50, Amyloidosis, Porphyria, and Other Specified Metabolic Disorders

0.648

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 E74.03 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for E74.03

For E74.03 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 E74.03 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

E74.03 is the ICD-10-CM diagnosis code for cori disease. A rare inherited metabolic disorder where the body cannot properly process glycogen due to debranching enzyme deficiency, causing muscle weakness and liver problems. E74.03 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 CMS-HCC V28 risk adjustment model, E74.03 maps to Amyloidosis, Porphyria, and Other Specified Metabolic Disorders (HCC 50) with a community, non-dual, aged base RAF weight of 0.648. Under the older CMS-HCC V24 model, E74.03 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.

Also known as Forbes disease; document presence of hepatomegaly and muscle symptoms. Because E74.03 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 E74.03 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Also known as Forbes disease; document presence of hepatomegaly and muscle symptoms
•This condition typically has a better prognosis than other glycogen storage diseases

Clinical Significance

Cori disease (Glycogen Storage Disease Type III), also known as Forbes disease, is caused by glycogen debranching enzyme deficiency. It primarily affects the liver and muscles, causing hepatomegaly, hypoglycemia, and progressive myopathy. While generally milder than von Gierke disease, it can lead to liver cirrhosis and cardiomyopathy in adulthood. Accurate capture ensures risk adjustment reflects the ongoing monitoring and dietary management needs.

Documentation Requirements

✓Confirmed diagnosis of Cori disease, Forbes disease, or GSD Type III
✓Enzyme assay or genetic testing confirming debranching enzyme deficiency
✓Subtype specification if documented (IIIa — liver and muscle; IIIb — liver only)
✓Physical exam findings including hepatomegaly and muscle weakness assessment
✓Laboratory values including creatine kinase, liver enzymes, and fasting glucose
✓Current dietary management and monitoring plan

Commonly Confused Codes

•E74.01: von Gierke disease (Type I): also causes hepatomegaly and hypoglycemia but involves different enzyme
•E74.00: Glycogen storage disease, unspecified: do not use when Cori disease is confirmed
•E74.04: McArdle disease (Type V): pure muscle GSD without liver involvement
•E74.09: Other glycogen storage disease: for GSD types without individual codes
•K76.89: Other specified diseases of liver: hepatic complications should be coded separately