What is ICD-10 code E71.521?

E71.521 is the ICD-10-CM diagnosis code for Adolescent X-linked adrenoleukodystrophy. A genetic disorder affecting males where nervous system deterioration begins in adolescence, causing progressive problems with movement, behavior, and cognitive function. It belongs to the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89). E71.521 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. E71.521 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. E71.521 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. E71.521 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 E71.521?

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. E71.521 was a payment HCC under V24 (Other Significant Endocrine and Metabolic Disorders) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting E71.521?

Document age of onset in adolescence (typically 10-21 years) to distinguish from childhood form which presents earlier This form generally has slower progression than childhood cerebral form; document specific neurological symptoms and functional decline Because E71.521 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.

E71.521: Adolescent X-linked adrenoleukodystrophy — ICD-10 | Other Significant Endocrine

ICD-10-CM Code View

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Code lookupE71.521Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

E71.521

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

Adolescent X-linked adrenoleukodystrophy

A genetic disorder affecting males where nervous system deterioration begins in adolescence, causing progressive problems with movement, behavior, and cognitive function.

Buddy Insight

Adolescent X-linked adrenoleukodystrophy presents in males between ages 10-21 with similar but generally slower-progressing cerebral demyelination compared to the childhood form.

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Mapped

HCC 23

Other Significant Endocrine a...

RAF 0.230

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 23

Other Significant Endocrine a...

RAF 0.0

RXHCC

Mapped

HCC 43

Other Significant Endocrine a...

RAF 0.0

Code Trumping

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Code Book Path

Official

E71.5Peroxisomal disorders

E71.52X-linked adrenoleukodystrophy

E71.521Adolescent X-linked adrenoleukodystrophy

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for E71.521 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for E71.521 in this effective period.

Related Child Codes

Official

E71.520Childhood cerebral X-linked adrenoleukodystrophy

E71.522Adrenomyeloneuropathy

E71.528Other X-linked adrenoleukodystrophy

E71.529X-linked adrenoleukodystrophy, unspecified type

Includes

Official

ICD-10-CM does not list Includes notes for E71.521 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for E71.521 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for E71.521 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for E71.521 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for E71.521 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Document age of symptom onset in adolescence, MRI findings and Loes score, very long chain fatty acid levels, ABCD1 gene mutation, adrenal function, and neurological assessment documenting rate of progression.

Record family history and carrier status testing of female relatives.

MEAT Support

HCC Buddy guidance

Record family history and carrier status testing of female relatives.

Audit Caution

HCC Buddy guidance

Distinguish from the childhood form by documented age of onset.

The clinical presentation may overlap, so ensure documentation specifies adolescent onset.

Some patients initially present with adrenal insufficiency before neurological symptoms appear.

Common Mistakes

HCC Buddy guidance

E71.520 (Childhood cerebral X-linked adrenoleukodystrophy) which presents earlier with faster progression

E71.522 (Adrenomyeloneuropathy) which predominantly affects the spinal cord rather than cerebral white matter

E71.529 (X-linked adrenoleukodystrophy, unspecified type) when the form cannot be determined.

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 E71.521 an HCC code?

Yes. E71.521 maps to Other Significant Endocrine and Metabolic Disorders under the V24 model but is not retained in V28.

HCC Category Mapping

V24HCC 23, Other Significant Endocrine and Metabolic Disorders

0.230

ESRDHCC 23, Other Significant Endocrine and Metabolic Disorders

0.000

RxHCCHCC 43, Other Significant Endocrine and Metabolic Disorders

0.000

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 E71.521 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for E71.521

For E71.521to 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 E71.521 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

E71.521 is the ICD-10-CM diagnosis code for adolescent x-linked adrenoleukodystrophy. A genetic disorder affecting males where nervous system deterioration begins in adolescence, causing progressive problems with movement, behavior, and cognitive function. E71.521 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, E71.521 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.

Document age of onset in adolescence (typically 10-21 years) to distinguish from childhood form which presents earlier. Because E71.521 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 E71.521 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Document age of onset in adolescence (typically 10-21 years) to distinguish from childhood form which presents earlier
•This form generally has slower progression than childhood cerebral form; document specific neurological symptoms and functional decline

Clinical Significance

Adolescent X-linked adrenoleukodystrophy presents in males between ages 10-21 with similar but generally slower-progressing cerebral demyelination compared to the childhood form. Patients develop cognitive decline, behavioral changes, vision and hearing impairment, and progressive motor dysfunction. Like the childhood form, early stem cell transplantation may halt progression if detected before significant neurological damage occurs.

Documentation Requirements

✓Document age of symptom onset in adolescence, MRI findings and Loes score, very long chain fatty acid levels, ABCD1 gene mutation, adrenal function, and neurological assessment documenting rate of progression.
✓Record family history and carrier status testing of female relatives.

Commonly Confused Codes

•E71.520 (Childhood cerebral X-linked adrenoleukodystrophy) which presents earlier with faster progression
•E71.522 (Adrenomyeloneuropathy) which predominantly affects the spinal cord rather than cerebral white matter
•E71.529 (X-linked adrenoleukodystrophy, unspecified type) when the form cannot be determined.