2026 ICD-10-CM Diagnosis Code M33.12Other dermatomyositis with myopathy

ICD-10-CM Codes›M00–M99›M30-M36›M33

ICD-10-CM M33.12
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M33.12 is a billable ICD-10-CM diagnosis code for other dermatomyositis with myopathy. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 545 through 547. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 126 closely related codes. Coders also document this condition as calcification of muscle due to adult dermatomyositis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Systemic lupus erythematosus and connective tissue disorders.

For Medicare Advantage risk adjustment, M33.12 maps to CMS-HCC Category 93 (Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders) under the V28 model, adding a risk factor of about 0.617 for a community, non-dual, aged beneficiary in payment year 2026.

Code Identity

ICD-10-CM Code
M33.12
Billable Status
Yes — Valid for Submission
Code Describes
Other dermatomyositis with myopathy
Short Description
Other dermatomyositis with myopathy
Same as the full description in the CMS dataset.
Parent Code
M33.1
Other dermatomyositis

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM30-M36Systemic connective tissue disorders
CategoryM33Dermatopolymyositis
This CodeM33.12Other dermatomyositis with myopathy

Medicare Risk Adjustment (HCC)Billing

M33.12 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 2026.

CMS-HCC V28 Category (Payment Model)
HCC 93— Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders
Payment HCC · PY 2026 one of 508 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.617
community, non-dual, aged · ranges 0.288–0.617 across segments
Hierarchy
Supersedes HCC 94
less severe related categories are not paid alongside HCC 93
Prior Model (CMS-HCC V24)
HCC 40
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 40 · ESRD (V21): HCC 40 · ESRD (V21): HCC 75 · ESRD (V24): HCC 40
ESRD V21 weights: 0.072 dialysis, 0.274–0.398 functioning graft · ESRD V21 weights: 0.059 dialysis, 0.284–0.323 functioning graft · ESRD V24 weights: 0.058 dialysis, 0.284–0.414 functioning graft
Part D (RxHCC)
RxHCC 83 — Rheumatoid Arthritis and Other Inflammatory Polyarthropathy
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2026 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.

  • Calcification of muscle due to adult dermatomyositis
  • Calcinosis due to adult type dermatomyositis

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.

CCSR MUS024
Systemic lupus erythematosus and connective tissue disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Dermatomyositis

    a subacute or chronic inflammatory disease of muscle and skin, marked by proximal muscle weakness and a characteristic skin rash. the illness occurs with approximately equal frequency in children and adults. the skin lesions usually take the form of a purplish rash (or less often an exfoliative dermatitis) involving the nose, cheeks, forehead, upper trunk, and arms. the disease is associated with a complement mediated intramuscular microangiopathy, leading to loss of capillaries, muscle ischemia, muscle-fiber necrosis, and perifascicular atrophy. the childhood form of this disease tends to evolve into a systemic vasculitis. dermatomyositis may occur in association with malignant neoplasms. (from adams et al., principles of neurology, 6th ed, pp1405-6)

  • Adult Dermatomyositis

    dermatomyositis in an adult.

  • Childhood Dermatomyositis|JDM|JDM|Juvenile Dermatomyositis|Juvenile Dermatomyositis

    an inflammatory myopathy of childhood resulting in muscle weakness, and associated with a characteristic skin rash.

  • Cutaneous Dermatomyositis Disease Area and Severity Index|CDASI|CDASI

    an instrument that measures activity and damage in the skin of dermatomyositis patients.

  • Dermatomyositis

    inflammation of the skin and muscle.

  • Dermatomyositis Skin Severity Index|DSSI|DSSI

    an assessment of disease activity in the skin of patients with dermatomyositis.

  • Interferon-Induced Helicase C Domain-Containing Protein 1|CADM-140 Autoantigen|Clinically Amyopathic Dermatomyositis Autoantigen 140 kDa|EC 3.6.4.13|Helicard|Helicase with 2 CARD Domains|IFIH1|Interferon-Induced With Helicase C Domain Protein 1|MDA-5|Melanoma Differentiation Associated Protein-5|Melanoma Differentiation-Associated Protein 5|Murabutide Down-Regulated Protein|RLR-2|RNA Helicase-DEAD Box Protein 116

    interferon-induced helicase c domain-containing protein 1 (1025 aa, ~117 kda) is encoded by the human ifih1 gene. this protein is involved in the positive regulation of antiviral responses.

  • Juvenile Dermatomyositis Sine Myositis|Juvenile Amyopathic Dermatomyositis|Juvenile Amyopathic Dermatomyositis|Juvenile Dermatomyositis sine Myositis|Juvenile dermatomyositis without myopathy

    a rare form of juvenile dermatomyositis that manifests with characteristic cutaneous findings for at least six months in the absence of any detectable muscle involvement.

  • Juvenile Dermatomyositis with Myopathy|Juvenile dermatomyositis with myopathy

    evidence of juvenile dermatomyositis with myopathy.

  • Juvenile Dermatomyositis with Other Organ Involvement|Juvenile dermatomyositis with other organ involvement

    evidence of juvenile dermatomyositis with other organ involvement.

  • Juvenile Dermatomyositis with Respiratory Involvement|Juvenile dermatomyositis with respiratory involvement

    evidence of juvenile dermatomyositis with respiratory involvement.

  • Juvenile Dermatomyositis, Organ Involvement Unspecified|Juvenile dermatomyositis, organ involvement unspecified

    evidence of juvenile dermatomyositis, organ involvement unspecified.

  • Other Dermatomyositis with Myopathy|Other dermatomyositis with myopathy

    evidence of other dermatomyositis with myopathy not specified elsewhere.

  • Other Dermatomyositis with Other Organ Involvement|Other dermatomyositis with other organ involvement

    evidence of other dermatomyositis with other organ involvement not specified elsewhere.

  • Other Dermatomyositis with Respiratory Involvement|Other dermatomyositis with respiratory involvement

    evidence of other dermatomyositis with respiratory involvement not specified elsewhere.

  • Other Dermatomyositis without Myopathy|Other dermatomyositis without myopathy

    evidence of other dermatomyositis without myopathy not specified elsewhere.

  • Other Dermatomyositis, Organ Involvement Unspecified|Other dermatomyositis, organ involvement unspecified

    evidence of other dermatomyositis, organ involvement unspecified not specified elsewhere.

  • Chromodomain-Helicase-DNA-Binding Protein 3|ATP-Dependent Helicase CHD3|CHD-3|CHD3|Chromodomain Helicase DNA Binding Protein 3|Chromodomain Helicase DNA-Binding Protein 3|Dermatomyositis Autoantigen Mi-2 Alpha|EC 3.6.4.12|MI-2 ALPHA ANTIGEN|MI-2 Alpha|MI-2a|Mi-2 Alpha|Mi-2 Autoantigen 240 kDa Protein|Mi2-Alpha|Zinc Finger Helicase|hZFH

    chromodomain-helicase-dna-binding protein 3 (2000 aa, ~227 kda) is encoded by the human chd3 gene. this protein is involved in chromatin remodeling, spindle organization during mitosis and transcriptional repression.

  • Chromodomain-Helicase-DNA-Binding Protein 4|ATP-Dependent Helicase CHD4|CHD-4|CHD4|Chromodomain Helicase DNA-Binding Protein 4|Dermatomyositis Autoantigen Mi-2 Beta|EC 3.6.4.12|MI-2 BETA ANTIGEN|MI-2 Beta|MI-2b|Mi-2 Autoantigen 218 kDa Protein|Mi-2 Beta|Mi2-Beta

    chromodomain-helicase-dna-binding protein 4 (1912 aa, ~218 kda) is encoded by the human chd4 gene. this protein is involved in chromatin remodeling.

  • MI-2 Antigens|Dermatomyositis Autoantigen Mi-2|MI-2 ANTIGENS|Major Dermatomyositis-specific Mi-2 Autoantigen

    antigens derived from certain helicases in the nucleosome remodeling-deacetylase complex (nurd) involved in transcription regulation that may be comprised of (but not limited to) two isoforms mi-2 alpha and mi-2 beta. they can be considered as autoantigens and are commonly associated with systemic autoimmune myopathy dermatomyositis.

Patient EducationClinical

Myositis

Myositis means inflammation of the muscles that you use to move your body. An injury, infection, or autoimmune disease can cause it. Two specific kinds are polymyositis and dermatomyositis. Polymyositis causes muscle weakness, usually in the muscles closest to the trunk of your body.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert M33.12 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
710.3 Dermatomyositis
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.
ICD-9-CM
359.6 Infl myopathy in oth dis
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About M33.12Overview

What is the ICD-10 code for other dermatomyositis with myopathy?

The ICD-10-CM code for other dermatomyositis with myopathy is M33.12 (sometimes written as M3312). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is M33.12 (Other dermatomyositis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other dermatomyositis with myopathy on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M33.12 group to?

When other dermatomyositis with myopathy is the principal diagnosis on an inpatient stay, it groups to MS-DRG 545, 546, 547, with relative weights from 0.8362 to 2.4817 depending on complications. Higher weights mean higher Medicare reimbursement.

Is M33.12 a CC or MCC?

CMS lists M33.12 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 126 closely related codes in its exclusion list.

What is the ICD-9 equivalent of M33.12?

Under the General Equivalence Mappings, other dermatomyositis with myopathy converts to ICD-9-CM 710.3 (dermatomyositis) and 359.6 (infl myopathy in oth dis). The mapping is approximate, so confirm the match fits the documentation.

What HCC is M33.12?

M33.12 (other dermatomyositis with myopathy) maps to CMS-HCC Category 93 (Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders), commonly written as HCC 93, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 40 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 83.

Does M33.12 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, M33.12 adds a risk adjustment factor of about 0.617 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.288 to 0.617 depending on the payment segment). HCC 93 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 93 category page.