Skip to content
HCC Buddy home

B01.12 ICD-10-CM Code: Varicella myelitis

B01.12 maps to CMS-HCC V28 182 (RAF 0.478). Documentation must support MEAT. MEAT criteria · RAF calculator · free HCC coding tools

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.

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Viral infections characterized by skin and mucous membrane lesions (B00-B09)

B01.12

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

Varicella myelitis

Chickenpox virus infection affecting the spinal cord, causing inflammation that may lead to weakness or loss of function in affected areas.

Buddy the Bee presenting code insight

Buddy Insight

Varicella myelitis is spinal cord inflammation caused by the chickenpox virus (varicella-zoster virus), typically occurring as a rare complication of primary varicella infection or reactivation.

CMS-HCC V28

HCC 182

RAF 0.478

CMS-HCC V24

HCC 72

RAF 0.481

ACA/HHS

HCC 110

Varies by metal level

ESRD/PACE

HCC 72

RAF 0.099

RXHCC

HCC 155

RAF 0.086

Code Book Path

Official
B01Varicella [chickenpox]
B01.1Varicella encephalitis, myelitis and encephalomyelitis
B01.12Varicella myelitis

Inclusion Terms

Official
  • Postchickenpox myelitis

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for B01.12 in this effective period.

Related Child Codes

Official
B01.11Varicella encephalitis and encephalomyelitis

Includes

Official

ICD-10-CM does not list Includes notes for B01.12 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for B01.12 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for B01.12 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for B01.12 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for B01.12 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
VZV confirmed by CSF PCR or positive VZV IgM antibodies
Active or recent varicella infection documented (rash, exposure history)
MRI findings showing spinal cord inflammation pattern
Spinal level and extent of myelitis documented

MEAT Support

HCC Buddy guidance
VZV confirmed by CSF PCR or positive VZV IgM antibodies
Active or recent varicella infection documented (rash, exposure history)
MRI findings showing spinal cord inflammation pattern
Spinal level and extent of myelitis documented

Audit Caution

HCC Buddy guidance
Confusing varicella myelitis (B01.12, primary infection) with postherpetic myelitis (B02.24, reactivation) — these have different codes and clinical contexts
Not distinguishing between HSV and VZV myelitis, which require viral-specific testing to differentiate
Using generic myelitis codes when the varicella etiology has been confirmed
Coding varicella encephalitis (B01.11) when the infection specifically affects the spinal cord rather than the brain

Common Mistakes

HCC Buddy guidance
B00.82 (Herpes simplex myelitis) — HSV myelitis is caused by herpes simplex, not varicella-zoster; viral PCR differentiates these
B02.24 (Postherpetic myelitis) — Occurs after herpes zoster (shingles) reactivation in adults; B01.12 is during primary varicella infection
G04.89 (Other myelitis) — Generic myelitis code; use B01.12 when VZV is confirmed as the cause

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 B01.12 an HCC code?

Yes. B01.12 (Varicella myelitis) maps to Spinal Cord Disorders/Injuries under the CMS-HCC V28 risk adjustment model (and Spinal Cord Disorders/Injuries under V24), with a community non-dual aged RAF of 0.478. It is billable for payment year 2026.

Coder answer: B01.12 is billable and maps to V28 HCC 182, Spinal Cord Disorders/Injuries. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
B01.12
Description
Varicella myelitis
HCC (V28)
HCC 182 — Spinal Cord Disorders/Injuries
RAF
0.478
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 182, Spinal Cord Disorders/Injuries
0.478
V24HCC 72, Spinal Cord Disorders/Injuries
0.481
ESRDHCC 72, Spinal Cord Disorders/Injuries
0.099
RxHCCHCC 155, Myelitis and Encephalomyelitis
0.086

Each model's RAF is its CMS base weight for that model's standard population, so 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 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.

Work B01.12 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for B01.12

For B01.12 to 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 B01.12 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

Get the V28 RAF + MEAT cheat sheet

One printable page: confirm a code's V28 HCC status, its RAF weight, and the MEAT your note needs to make it stick. Free, no card.

Free PDF. No card. Unsubscribe anytime.

What This Code Means

B01.12 is the ICD-10-CM diagnosis code for varicella myelitis. Chickenpox virus infection affecting the spinal cord, causing inflammation that may lead to weakness or loss of function in affected areas. B01.12 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering viral infections characterized by skin and mucous membrane lesions (b00-b09).

Under the CMS-HCC V28 risk adjustment model, B01.12 maps to Spinal Cord Disorders/Injuries (HCC 182) with a community, non-dual, aged base RAF weight of 0.478. Under the older V24 model, B01.12 mapped to the same category but with a base RAF weight of 0.481, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Distinguish from B00.82 (herpes simplex myelitis) which is caused by HSV-1 or HSV-2. Because B01.12 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for B01.12 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Distinguish from B00.82 (herpes simplex myelitis) which is caused by HSV-1 or HSV-2
  • •Document the level and extent of spinal cord involvement if available

Clinical Significance

Varicella myelitis is spinal cord inflammation caused by the chickenpox virus (varicella-zoster virus), typically occurring as a rare complication of primary varicella infection or reactivation. This represents a serious neurological emergency that can cause permanent spinal cord damage if not treated promptly with antiviral therapy.

Documentation Requirements

  • ✓VZV confirmed by CSF PCR or positive VZV IgM antibodies
  • ✓Active or recent varicella infection documented (rash, exposure history)
  • ✓MRI findings showing spinal cord inflammation pattern
  • ✓Spinal level and extent of myelitis documented
  • ✓Neurological status: motor function, sensory level, bladder/bowel involvement

Commonly Confused Codes

  • •B00.82 (Herpes simplex myelitis): HSV myelitis is caused by herpes simplex, not varicella-zoster; viral PCR differentiates these
  • •B02.24 (Postherpetic myelitis): Occurs after herpes zoster (shingles) reactivation in adults; B01.12 is during primary varicella infection
  • •G04.89 (Other myelitis): Generic myelitis code; use B01.12 when VZV is confirmed as the cause

Child Codes

B01.11Varicella encephalitis and encephalomyelitis
B01.12Varicella myelitis
HCC 182

Code Hierarchy

└B01Varicella [chickenpox]└B01.1Varicella encephalitis, myelitis and encephalomyelitis└B01.12Varicella myelitis
└B01.12Varicella myelitis

Because B01.12 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

B01.12 maps to CMS-HCC V28 category 182, Spinal Cord Disorders/Injuries. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. Because B01.12 carries a payment HCC, you can see what it adds to a RAF score and check the documentation the chart needs before it is submitted.

Work B01.12 in HCC Buddy

Open B01.12 in the Code Book for the full Index-to-Tabular path, MEAT checklist, and V28 HCC mapping, or in the Encoder to code from a keyword search. Pro includes 7 days to try everything, no card required.

Open in Code BookOpen in EncoderStart Pro