F78.A1
BillableSYNGAP1-related intellectual disability
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is F78.A1 an HCC code?
No. F78.A1 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.A1
For F78.A1to 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.A1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
F78.A1 is the ICD-10-CM diagnosis code for syngap1-related intellectual disability. A genetic developmental condition caused by mutations in the SYNGAP1 gene, resulting in intellectual disability of varying severity along with potential behavioral, neurological, and developmental challenges. F78.A1 sits in the ICD-10-CM chapter for mental, behavioral and neurodevelopmental disorders (f01-f99), within the section covering intellectual disabilities (f70-f79).
F78.A1 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.A1 does not map to any HCC in V28 or V24 models. RxHCC maps to RxHCC 147 (0.000 weight). No direct RAF score impact, but the specific genetic code enables rare disease tracking and potential clinical trial identification. Coders reviewing F78.A1 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.A1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document genetic testing results confirming SYNGAP1 mutation in the medical record
- •Specify the severity level of intellectual disability (mild, moderate, severe, or profound) if determined
Clinical Significance
SYNGAP1-related intellectual disability is a specific genetic form caused by mutations in the SYNGAP1 gene, which plays a critical role in synaptic function and neurodevelopment. It typically presents with moderate to severe intellectual disability, epilepsy (often treatment-resistant), and autism spectrum features. This is a relatively newly recognized genetic etiology with an ICD-10-CM code that allows for precise tracking of this rare condition for research and treatment development purposes.
Documentation Requirements
- ✓Genetic testing results confirming a pathogenic or likely pathogenic variant in the SYNGAP1 gene
- ✓Provider documentation linking the intellectual disability to the SYNGAP1 mutation
- ✓Documentation of the severity of intellectual disability and associated features (epilepsy, behavioral issues)
- ✓Current treatment plan including anti-epileptic medications if applicable
- ✓Genetic counseling documentation if relevant
Code Also
Commonly Confused Codes
- •F78.A9 — Other genetic related intellectual disability; use F78.A1 specifically when SYNGAP1 is identified
- •F71 — Moderate intellectual disabilities; when the genetic etiology is known (SYNGAP1), use F78.A1 rather than severity-only codes
- •G40.x — Epilepsy codes; epilepsy associated with SYNGAP1 should be coded separately in addition to F78.A1
- •F84.0 — Autistic disorder; autism features in SYNGAP1 are coded additionally if they meet diagnostic criteria