What is ICD-10 code F78.A9?

F78.A9 is the ICD-10-CM diagnosis code for Other genetic related intellectual disability. Intellectual disability caused by genetic factors that don't fit into other specific genetic categories. This represents a significant limitation in intellectual functioning and adaptive behavior due to inherited genetic conditions. F78.A9 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. F78.A9 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. F78.A9 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. F78.A9 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.

Which HCC does F78.A9 map to under V28?

F78.A9 has no payable CMS-HCC V28 mapping in the final FY2026 CMS file.

What RAF reference is published for F78.A9?

F78.A9 has no V28 reference coefficient because the final FY2026 source verifies no payable V28 mapping.

What is the V28 vs V24 difference for F78.A9?

F78.A9 has verified no payable V28 mapping in the final FY2026 source. Select a historical effective period before making any V24 comparison.

What documentation supports F78.A9?

Use this code only after ruling out other specific genetic intellectual disability codes (F78.A0-F78.A8) Document the genetic condition or syndrome when possible to support medical necessity and potential future specificity F78.A9 is not a CMS-HCC V28 payment code in the verified current source, so MEAT is not the payment hook. Documentation still has to support the diagnosis if you report it.

2026 ICD-10-CM F78.A9: Other genetic related intellectual

F78.A9 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · HCC coding software

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupF78.A9

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Mental, Behavioral and Neurodevelopmental disorders (F01-F99) / Intellectual Disabilities (F70-F79)

F78.A9

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

Other genetic related intellectual disability

Intellectual disability caused by genetic factors that don't fit into other specific genetic categories. This represents a significant limitation in intellectual functioning and adaptive behavior due to inherited genetic conditions.

Buddy Insight

This code captures intellectual disability with a confirmed genetic etiology that is not SYNGAP1 (which has its own code at F78.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

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 148

Mild or Unspecified Intellect...

Code-level coefficient reference

Code Book Path

Official

F78Other intellectual disabilities F78.AOther genetic related intellectual disabilities F78.A9Other genetic related intellectual disability

Inclusion Terms

Official

No inclusion terms are included in this display for F78.A9. Check the code and parent instructions in the Code Book.

Excludes 2

Official

symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)Inherited from F01-F99

Related Codes

Official

F78.A1SYNGAP1-related intellectual disability

Includes

Official

disorders of psychological developmentInherited from F01-F99

Excludes 1

Official

borderline intellectual functioning, IQ above 70 to 84 (R41.83)Inherited from F70-F79

Code First

Official

any associated physical or developmental disordersInherited from F70-F79

Use Additional

Official

No Use Additional Code instructions are included in this display for F78.A9. Check the code and parent instructions in the Code Book.

Code Also

Official

, if applicable, any associated disorders

Buddy Documentation Tip

HCC Buddy guidance

Genetic testing results confirming a genetic cause of intellectual disability (other than SYNGAP1)

Provider documentation linking the intellectual disability to the identified genetic finding

Specification of the genetic condition if possible in the clinical notes

Documentation of intellectual disability severity and associated features

MEAT Support

HCC Buddy guidance

Genetic testing results confirming a genetic cause of intellectual disability (other than SYNGAP1)

Provider documentation linking the intellectual disability to the identified genetic finding

Specification of the genetic condition if possible in the clinical notes

Documentation of intellectual disability severity and associated features

Audit Caution

HCC Buddy guidance

Using F78.A9 when the genetic condition has its own specific ICD-10-CM code (Down syndrome, Fragile X, etc.)

Failing to also code the specific genetic syndrome when one exists alongside the intellectual disability code

Using unspecified intellectual disability (F79) when genetic testing has confirmed a genetic cause

Not updating coding when genetic test results return after an initial encounter

Common Mistakes

HCC Buddy guidance

F78.A1 — SYNGAP1-related intellectual disability; use F78.A1 if the specific gene is SYNGAP1

Q90.x — Down syndrome; Down syndrome has its own specific codes and should not use F78.A9

Q87.x — Other specified congenital malformation syndromes; many genetic syndromes have specific codes

F79 — Unspecified intellectual disabilities; use F78.A9 when genetic etiology is confirmed, not the unspecified code

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 F78.A9 an HCC code?

F78.A9 is not in the CMS-HCC V28 or V24 community payment model. F78.A9 has a separate mapping under the Part D RxHCC model (HCC 148 (Mild or Unspecified Intellectual Disability/Developmental Disorder)); the applicable result needs member context.

Code: F78.A9
Description: Other genetic related intellectual disability
HCC (V28): No CMS-HCC V28 mapping
RAF reference coefficient: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

RxHCCHCC 148, Mild or Unspecified Intellectual Disability/Developmental Disorder

Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work F78.A9 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for F78.A9

For F78.A9, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

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

Coder workflow notes

Get the V28 mapping + MEAT cheat sheet

One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.

Free PDF. No card. Unsubscribe anytime.

What This Code Means

F78.A9 is the ICD-10-CM diagnosis code for other genetic related intellectual disability. Intellectual disability caused by genetic factors that don't fit into other specific genetic categories. This represents a significant limitation in intellectual functioning and adaptive behavior due to inherited genetic conditions. F78.A9 sits in the ICD-10-CM chapter for mental, behavioral and neurodevelopmental disorders (f01-f99), within the section covering intellectual disabilities (f70-f79).

F78.A9 has no mapping under the CMS-HCC V28 or V24 community payment models. F78.A9 has a separate mapping under the Part D RxHCC model (HCC 148 (Mild or Unspecified Intellectual Disability/Developmental Disorder)); the applicable result needs member context. Do not assign V28 risk adjustment value from this page; verify the applicable model and payment year before using this code for risk adjustment.

Use this code only after ruling out other specific genetic intellectual disability codes (F78.A0-F78.A8).

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for F78.A9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use this code only after ruling out other specific genetic intellectual disability codes (F78.A0-F78.A8)
•Document the genetic condition or syndrome when possible to support medical necessity and potential future specificity

Clinical Significance

This code captures intellectual disability with a confirmed genetic etiology that is not SYNGAP1 (which has its own code at F78.A1). This includes intellectual disability caused by other single-gene mutations, chromosomal microdeletions/duplications, or other genetic conditions not elsewhere classified. Documenting the genetic basis supports research, family counseling, and targeted management approaches.

Documentation Requirements

✓Genetic testing results confirming a genetic cause of intellectual disability (other than SYNGAP1)
✓Provider documentation linking the intellectual disability to the identified genetic finding
✓Specification of the genetic condition if possible in the clinical notes
✓Documentation of intellectual disability severity and associated features
✓Genetic counseling documentation and family history assessment

Code Also

, if applicable, any associated disorders

Commonly Confused Codes

•F78.A1: SYNGAP1-related intellectual disability; use F78.A1 if the specific gene is SYNGAP1
•Q90.x: Down syndrome; Down syndrome has its own specific codes and should not use F78.A9
•Q87.x: Other specified congenital malformation syndromes; many genetic syndromes have specific codes
•F79: Unspecified intellectual disabilities; use F78.A9 when genetic etiology is confirmed, not the unspecified code

Child Codes

F78.A1SYNGAP1-related intellectual disability

F78.A9Other genetic related intellectual disability

Code Hierarchy

└F78Other intellectual disabilities └F78.AOther genetic related intellectual disabilities └F78.A9Other genetic related intellectual disability

└F78.A9Other genetic related intellectual disability

HCC Buddy Code Card

F78.A9

Is F78.A9 an HCC code?

HCC Category Mapping

MEAT review for F78.A9

Get the V28 mapping + MEAT cheat sheet

What This Code Means

Coding Tips

Clinical Significance

Documentation Requirements

Code Also

Commonly Confused Codes

Child Codes

Code Hierarchy

F78.A9 code history

Work F78.A9 in HCC Buddy

F78.A9 ICD-10-CM Code: Other genetic related intellectual disability

HCC Buddy Code Card

F78.A9

Is F78.A9 an HCC code?

HCC Category Mapping

MEAT review for F78.A9

Get the V28 mapping + MEAT cheat sheet

What This Code Means

Coding Tips

Clinical Significance

Documentation Requirements

Code Also

Commonly Confused Codes

Child Codes

Code Hierarchy

F78.A9 code history

Work F78.A9 in HCC Buddy