2027 ICD-10-CM Diagnosis Code B01.12Varicella myelitis
ICD-10-CM Codes›A00–B99›B00-B09›B01
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 182
- Not Chronic
B01.12 is a billable ICD-10-CM diagnosis code for varicella myelitis. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 23 through 24, 97 through 99. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 31 closely related codes. Coders also document this condition as post-infective myelitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Viral infection.
For Medicare Advantage risk adjustment, B01.12 maps to CMS-HCC Category 182 (Spinal Cord Disorders/Injuries) under the V28 model, adding a risk factor of about 0.478 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
B01.12 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Post-infective myelitis
- Postvaricella myelitis
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to B01.12: its own notes plus those printed at Chapter 1. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- diseases generally recognized as communicable or transmissible
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Postchickenpox myelitis
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- carrier or suspected carrier of infectious disease (Z22.-)
- certain localized infections - see body system-related chapters
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
- infectious and parasitic diseases specific to the perinatal period (P35-P39)
- influenza and other acute respiratory infections (J00-J22)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify resistance to antimicrobial drugs (Z16.-)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name B01.12, its category, or a range that includes it.
Excludes1 2
These codes carry an Excludes1 note naming B01.12: they are not reported together with it, unless the two conditions are unrelated.
- G04.01 Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)post chickenpox encephalitis (B01.1) names B01.1, which includes this code
- G05 Encephalitis, myelitis and encephalomyelitis in diseases classified elsewherepostchickenpox encephalitis, myelitis and encephalomyelitis (B01.1-) names B01.1-, which includes this code
Excludes2 2
These codes carry an Excludes2 note naming B01.12: its condition is not part of those codes, and both may be reported when the patient has both.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Chickenpox
Chickenpox is an infection caused by the varicella-zoster virus. Most cases are in children under age 15, but older children and adults can get it. It spreads very easily from one person to another.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert B01.12 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About B01.12Overview
What is the ICD-10 code for varicella myelitis?
The ICD-10-CM code for varicella myelitis is B01.12 (sometimes written as B0112). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is B01.12 (Varicella encephalitis, myelitis and encephalomyelitis) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report varicella myelitis on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does B01.12 group to?
When varicella myelitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 24, 98, 99, 23, 97, with relative weights from 1.5249 to 5.7422 depending on complications. Higher weights mean higher Medicare reimbursement.
Is B01.12 a CC or MCC?
CMS lists B01.12 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 31 closely related codes in its exclusion list.
What is the ICD-9 equivalent of B01.12?
Under the General Equivalence Mappings, varicella myelitis converts to ICD-9-CM 052.2 (postvaricella myelitis). The mapping is a direct match.
What HCC is B01.12?
B01.12 (varicella myelitis) maps to CMS-HCC Category 182 (Spinal Cord Disorders/Injuries), commonly written as HCC 182, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 72 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 155.
Does B01.12 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, B01.12 adds a risk adjustment factor of about 0.478 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.270 to 0.478 depending on the payment segment). A more severe related category (HCC 180, HCC 181, HCC 191, and HCC 192) supersedes it when both are reported. See the full factor table on the HCC 182 category page.
