Q93.0
BillableWhole chromosome monosomy, nonmosaicism (meiotic nondisjunction)
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is Q93.0 an HCC code?
No. Q93.0 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 Q93.0
For Q93.0to 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 Q93.0 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
Q93.0 is the ICD-10-CM diagnosis code for whole chromosome monosomy, nonmosaicism (meiotic nondisjunction). A chromosomal condition where a person is missing an entire chromosome (has only one copy instead of the normal two), affecting all cells in the body. Q93.0 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).
Q93.0 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 severe chromosomal abnormalities who typically require multiple specialized medications for associated conditions.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Q93.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Monosomy of entire autosomes is usually lethal; most commonly seen in Turner syndrome (45,X)
- •Specify which chromosome is affected if documented
Clinical Significance
Whole chromosome monosomy represents a severe chromosomal abnormality where an entire chromosome is missing from all cells, typically resulting in significant developmental abnormalities, intellectual disabilities, and often life-threatening complications. This condition requires comprehensive medical management and genetic counseling for affected families.
Documentation Requirements
- ✓Karyotype analysis confirming whole chromosome monosomy
- ✓Specific chromosome missing (if identified)
- ✓Nonmosaic pattern documented
- ✓Clinical manifestations and abnormalities
- ✓Associated congenital anomalies
- ✓Developmental assessment findings
- ✓Genetic counseling provided
- ✓Meiotic nondisjunction mechanism documented