2026 ICD-10-CM Diagnosis Code M35.1Other overlap syndromes
ICD-10-CM Codes›M00–M99›M30-M36›M35
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Chronic Condition
M35.1 is a billable ICD-10-CM diagnosis code for other overlap syndromes. 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 6 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Systemic lupus erythematosus and connective tissue disorders.
M35.1 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 40 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 40, ESRD (V21) category 40, ESRD (V24) category 40, and RxHCC Part D (V08) category 84 for payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
M35.1 no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.
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.
- Childhood type dermatomyositis
- Connective tissue disease overlap syndrome
- Dermatomyositis overlap syndrome
- Juvenile dermatomyositis overlap syndrome
- Lupus erythematosus overlap syndrome
- Overlap syndrome
- Polymyositis
- Polymyositis overlap syndrome
- Undifferentiated connective tissue disease
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Mixed connective tissue disease
Type 1 Excludes
- polyangiitis overlap syndrome M30.8
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Disease, diseased See Also: Syndrome;
mixed connective tissue M35.1
Syndrome See Also: Disease;
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
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)Polymyositis
diseases characterized by inflammation involving multiple muscles. this may occur as an acute or chronic condition associated with medication toxicity (drug toxicity); connective tissue diseases; infections; malignant neoplasms; and other disorders. the term polymyositis is frequently used to refer to a specific clinical entity characterized by subacute or slowly progressing symmetrical weakness primarily affecting the proximal limb and trunk muscles. the illness may occur at any age, but is most frequent in the fourth to sixth decade of life. weakness of pharyngeal and laryngeal muscles, interstitial lung disease, and inflammation of the myocardium may also occur. muscle biopsy reveals widespread destruction of segments of muscle fibers and an inflammatory cellular response. (adams et al., principles of neurology, 6th ed, pp1404-9)Exosome Component 10|Autoantigen PM-SCL|Autoantigen PM/Scl|EC 3.1.13.-|EXOSC10|P100 Polymyositis-Scleroderma Overlap Syndrome-Associated Autoantigen|PM/Scl-100|Polymyositis/Scleroderma Autoantigen 100 kDa|Polymyositis/Scleroderma Autoantigen 2
exosome component 10 (885 aa, ~101 kda) is encoded by the human exosc10 gene. this protein plays a role in the maturation and degradation of rna.Other Overlap Syndromes|Other overlap syndromes
evidence of other overlap syndromes not specified elsewhere.Overlap Syndrome
an autoimmune, connective tissue disorder in which the patient exhibits features from two or more diseases. these typically include systemic sclerosis, dermatomyositis, polymyositis, rheumatoid arthritis, systemic lupus erythematosus, and sjogren syndrome; in pediatrics the respective pediatric entities are encountered.Scleroderma Polymyositis Overlap Syndrome|Scleroderma Polymyositis
a rare autoimmune disorder in which patients present with overlapping symptoms of systemic scleroderma and polymyositis or dermatomyositis.Exosome Complex Component RRP45|AMPA RECEPTORS|Autoantigen PM/Scl 1|EXOSC9|Exosome Component 9|GLuRs|P75 Polymyositis-Scleroderma Autoantigen|P75 Polymyositis-Scleroderma Overlap Syndrome Associated Autoantigen|P75 Polymyositis-Scleroderma Overlap Syndrome-Associated Autoantigen|PM/Scl-75|Polymyositis/Scleroderma Autoantigen 1|Polymyositis/Scleroderma Autoantigen 75 kDa
exosome complex component rrp45 (439 aa, ~49 kda) is encoded by the human exosc9 gene. this protein is involved in the regulation of the exoribonuclease activity of the exosome.Exosome Component 10|Autoantigen PM-SCL|Autoantigen PM/Scl|EC 3.1.13.-|EXOSC10|EXOSC10|P100 POLYMYOSITIS-SCLERODERMA AUTOANTIGEN|P100 Polymyositis-Scleroderma Overlap Syndrome-Associated Autoantigen|PM/Scl 2|PM/Scl-100|PM/Scl-100|Polymyositis/Scleroderma Autoantigen 100 kDa|Polymyositis/Scleroderma Autoantigen 2|Polymyositis/Scleroderma Autoantigen 2
exosome component 10 (885 aa, ~101 kda) is encoded by the human exosc10 gene. this protein plays a role in the maturation and degradation of rna.
Patient EducationClinical
Connective Tissue Disorders
Your connective tissue supports many different parts of your body, such as your skin, eyes, and heart. It is like a "cellular glue" that gives your body parts their shape and helps keep them strong. It also helps some of your tissues do their work. It is made of many kinds of proteins. Cartilage and fat are types of connective tissue.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert M35.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About M35.1Overview
What is the ICD-10 code for other overlap syndromes?
The ICD-10-CM code for other overlap syndromes is M35.1 (sometimes written as M351). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is M35.1 (Other systemic involvement of connective tissue) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other overlap syndromes on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does M35.1 group to?
When other overlap syndromes 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 M35.1 a CC or MCC?
CMS lists M35.1 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 6 closely related codes in its exclusion list.
What is the ICD-9 equivalent of M35.1?
Under the General Equivalence Mappings, other overlap syndromes converts to ICD-9-CM 710.8 (diff connect tis dis NEC). The mapping is approximate, so confirm the match fits the documentation.
Does M35.1 risk-adjust for Medicare Advantage payment?
Not for Medicare Advantage. M35.1 mapped to HCC 40 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 40 (Rheumatoid Arthritis and Inflammatory Connective Tissue Disease), ESRD (V21) category 40 (Rheumatoid Arthritis and Inflammatory Connective Tissue Disease), ESRD (V24) category 40 (Rheumatoid Arthritis and Inflammatory Connective Tissue Disease), and RxHCC Part D (V08) category 84 (Systemic Lupus Erythematosus and Other Systemic Connective Tissue Disorders).
