Is ICD-10-CM code M33 billable?

No, M33 (Dermatopolymyositis) is a non-billable ICD-10-CM code. It must be coded to a more specific subcategory before it can be used for reimbursement.

What chapter does ICD-10-CM code M33 belong to?

M33 belongs to Chapter 13 of the ICD-10-CM tabular list: M00–M99 (Diseases of the Musculoskeletal System and Connective Tissue).

M33Not billable, use a more specific code below

Dermatopolymyositis

In Systemic connective tissue disorders (M30-M36), chapter 13: Diseases of the Musculoskeletal System and Connective Tissue

19 billable codes under M33: all are a CC; all map to HCC 93 (Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders), HCC 280 (Chronic Obstructive Pulmonary Disease, Interstitial Lung Disorders, and Other Chronic Lung Disorders).A CC or MCC (major CC) is a secondary diagnosis that raises the MS-DRG payment. An HCC counts toward a Medicare Advantage patient's risk score.

Instructional notes

Also applies, from Systemic connective tissue disorders (M30-M36)

These notes sit on M30-M36 and apply to every code under it, including M33.

Includes: conditions that are coded here

autoimmune disease NOS
collagen (vascular) disease NOS
systemic autoimmune disease
systemic collagen (vascular) disease

Excludes1: not coded here, use a different code

autoimmune disease, single organ or single cell-type -code to relevant condition category

Official coding guidelines

From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.

Covers site and laterality, acute injury versus chronic musculoskeletal conditions, 7th characters for pathologic fractures, osteoporosis with or without current fracture, and multisystem inflammatory syndrome.

Site and laterality (page 60)
Acute traumatic versus chronic or recurrent musculoskeletal conditions (page 61)
Coding of Pathologic Fractures (page 61)
Osteoporosis (page 61)
Multisystem Inflammatory Syndrome (page 62)

Read Section I.C.13 (page 60)

All codes under M33

M33 can't be used on a claim. Pick a billable code below; grey headings group them.

M33 MS-DRGs

As the principal diagnosis, all 19 billable codes under M33 group to MS-DRG 545, 546, or 547 (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.

Other codes that refer to M33

Notes on these codes point to M33.

G72 Excludes1: dermatopolymyositis (M33.-)
M60-M63 Excludes1: dermatopolymyositis (M33.-)

About the condition

Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.

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. Dermatomyositis causes muscle weakness, plus a skin rash.

Code history

Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.