F78.A9
BillableOther genetic related intellectual disability
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is F78.A9 an HCC code?
No. F78.A9 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
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 F78.A9
For F78.A9to 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 F78.A9 during that encounter — not just copy-forwarded from a problem list.
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 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.
F78.A9 does not map to any HCC in V28 or V24 models. RxHCC maps to RxHCC 148 (0.000 weight). No direct RAF contribution. Value is in precision medicine documentation and genetic condition tracking. Coders reviewing F78.A9 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-leverage RAF improvement available within accurate coding.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, 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
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