Q93.51
BillableAngelman syndrome
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is Q93.51 an HCC code?
No. Q93.51 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 Q93.51
For Q93.51to 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 Q93.51 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
Q93.51 is the ICD-10-CM diagnosis code for angelman syndrome. Angelman syndrome is a genetic disorder caused by loss of function of the maternal UBE3A gene, characterized by developmental delays, intellectual disability, seizures, and a distinctive happy demeanor with frequent smiling and laughter. Q93.51 sits in the ICD-10-CM chapter for congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (q00-qa0), within the section covering chromosomal abnormalities, not elsewhere classified (q90-q99).
Q93.51 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.
This code maps to RxHCC 148 (Mild Intellectual Disabilities) with a RAF weight of 0.0 in the RxHCC model. While it doesn't contribute to risk adjustment scoring, it identifies patients with Angelman syndrome who typically require multiple medications including anticonvulsants, sleep aids, and medications for behavioral management.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Q93.51 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Angelman syndrome has multiple genetic causes (deletion, uniparental disomy, imprinting defect); the genetic mechanism may be documented separately
- •This condition often presents with seizures and behavioral characteristics; code associated seizure disorders separately if present
Clinical Significance
Angelman syndrome is a severe neurodevelopmental disorder characterized by intellectual disability, seizures, ataxia, and a distinctive happy demeanor with frequent laughter. This condition requires comprehensive neurological management including seizure control, physical therapy, and behavioral interventions due to the complex medical and developmental needs.
Documentation Requirements
- ✓Genetic testing confirming UBE3A gene deletion or mutation
- ✓Characteristic happy demeanor and frequent laughter
- ✓Seizure history and type
- ✓Ataxia and movement abnormalities
- ✓Speech development (typically absent or minimal)
- ✓Intellectual disability assessment
- ✓Sleep disturbances documented
- ✓Genetic counseling provided
Commonly Confused Codes
- •Q9352 — Phelan-McDermid syndrome involves different genetic mechanism and features
- •Q9359 — Use specific Angelman syndrome code when diagnosed
- •Q9381 — Velocardiofacial syndrome has different genetic cause and features
- •F84.0 — Autism spectrum disorder may overlap but Angelman has specific genetic cause