ICD-10-CM 2027
ICD-10 code for mixed connective tissue disease
From the official ICD-10-CM alphabetic index entry “Disease, diseased › mixed connective tissue”. Page updated September 29, 2026.
About coding mixed connective tissue disease
The ICD-10-CM code for mixed connective tissue disease is M35.1 (Other overlap syndromes).
Within M35, choose M35.1 (Other overlap syndromes) only when documentation doesn't support a more specific option: Sjogren syndrome (M35.0), Behcet's disease (M35.2), polymyalgia rheumatica (M35.3), diffuse (eosinophilic) fasciitis (M35.4), multifocal fibrosclerosis (M35.5), relapsing panniculitis [Weber-Christian] (M35.6), hypermobility syndrome (M35.7), other specified systemic involvement of connective tissue (M35.8) and 1 more.
Don't report M35.1 together with the conditions in its Excludes1 note: polyangiitis overlap syndrome (M30.8).
As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.
Don't confuse with (Excludes1 for M35.1)
- polyangiitis overlap syndrome (M30.8)
Common questions about mixed connective tissue disease ICD-10 codes
What is the ICD-10 code for mixed connective tissue disease?
- M35.1 — Other overlap syndromes.
Is M35.1 billable?
- Yes. M35.1 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can M35.1 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict M35.1 as a principal diagnosis.
Is M35.1 a CC or MCC?
- M35.1 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.