M33.91 ICD-10-CM Code: Dermatopolymyositis, unspecified with respiratory involvement
M33.91 maps to CMS-HCC V28 HCCs 93 and 280. Source-labeled RAF references are available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Systemic connective tissue disorders (M30-M36)
M33.91
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceDermatopolymyositis, unspecified with respiratory involvement
A rare autoimmune disease with features of both dermatomyositis and polymyositis, with respiratory system involvement such as lung inflammation.
Buddy Insight
Unspecified dermatopolymyositis with respiratory involvement represents a serious combination requiring immediate aggressive treatment and pulmonology consultation.
CMS-HCC V28
MappedHCC 93
Coefficient HCC 93: 0.617 (Community Non-Dual Aged (CNA)); HCC 280: 0.319 (Community Non-Dual Aged (CNA))
+ HCC 280
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 056
Code-level coefficient reference
+ HCC 162
ESRD/PACE
MappedHCC 40
Code-level coefficient reference
+ HCC 112
RXHCC
MappedHCC 83
Code-level coefficient reference
+ HCC 227
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for M33.91. Check the code and parent instructions in the Code Book.
Excludes 2
Official- arthropathic psoriasis (L40.5-)Inherited from M00-M99
- certain conditions originating in the perinatal period (P04-P96)Inherited from M00-M99
- certain infectious and parasitic diseases (A00-B99)Inherited from M00-M99
- compartment syndrome (traumatic) (T79.A-)Inherited from M00-M99
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from M00-M99
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from M00-M99
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from M00-M99
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from M00-M99
- neoplasms (C00-D49)Inherited from M00-M99
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from M00-M99
Related Codes
Includes
Official- autoimmune disease NOSInherited from M30-M36
- collagen (vascular) disease NOSInherited from M30-M36
- systemic autoimmune diseaseInherited from M30-M36
- systemic collagen (vascular) diseaseInherited from M30-M36
Excludes 1
Official- autoimmune disease, single organ or single cell-type -code to relevant condition categoryInherited from M30-M36
Code First
OfficialNo Code First sequencing instructions are included in this display for M33.91. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for M33.91. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for M33.91. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 M33.91 an HCC code?
Yes. M33.91 (Dermatopolymyositis, unspecified with respiratory involvement) maps to HCC 93, Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders and HCC 280, Chronic Obstructive Pulmonary Disease, Interstitial Lung Disorders, and Other Chronic Lung Disorders under the CMS-HCC V28 risk adjustment model, with source-labeled community non-dual aged reference coefficients HCC 93 0.617 and HCC 280 0.319. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: M33.91 is billable and maps to V28 HCC 93, Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders and HCC 280, Chronic Obstructive Pulmonary Disease, Interstitial Lung Disorders, and Other Chronic Lung Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- M33.91
- Description
- Dermatopolymyositis, unspecified with respiratory involvement
- HCC (V28)
- HCC 93 — Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders; HCC 280 — Chronic Obstructive Pulmonary Disease, Interstitial Lung Disorders, and Other Chronic Lung Disorders
- RAF reference coefficient
- HCC 93: 0.617; HCC 280: 0.319
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work M33.91 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for M33.91
For M33.91, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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What This Code Means
M33.91 is the ICD-10-CM diagnosis code for dermatopolymyositis, unspecified with respiratory involvement. A rare autoimmune disease with features of both dermatomyositis and polymyositis, with respiratory system involvement such as lung inflammation. M33.91 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering systemic connective tissue disorders (m30-m36).
Under the CMS-HCC V28 risk adjustment model, M33.91 maps to Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders (HCC 93) with a source-labeled community, non-dual, aged reference coefficient of 0.617. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Document respiratory manifestations including dyspnea, pulmonary function test results, or imaging findings. For M33.91, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for M33.91 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document respiratory manifestations including dyspnea, pulmonary function test results, or imaging findings
- •Consider additional coding for interstitial lung disease or other specific respiratory conditions
Clinical Significance
Unspecified dermatopolymyositis with respiratory involvement represents a serious combination requiring immediate aggressive treatment and pulmonology consultation. The respiratory complication significantly worsens prognosis and increases mortality risk.
Documentation Requirements
- ✓Evidence of inflammatory myopathy with skin involvement
- ✓Documentation of respiratory system involvement
- ✓Pulmonary function testing showing impairment
- ✓Chest imaging demonstrating lung changes
- ✓Documentation that specific myositis subtype is unclear
- ✓Treatment plan addressing respiratory complications
- ✓Monitoring plan for lung function
- ✓Coordination between rheumatology and pulmonology