M35.9Systemic involvement of connective tissue, unspecified

M35.9 is the ICD-10-CM diagnosis code for systemic involvement of connective tissue, unspecified. It belongs to category M35 (other systemic involvement of connective tissue), block M30-M36 (systemic connective tissue disorders) and chapter 13 (diseases of the musculoskeletal system and connective tissue). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within M35, choose M35.9 (Systemic involvement of connective tissue, unspecified) only when documentation doesn't support a more specific option: Sjogren syndrome (M35.0), other overlap syndromes (M35.1), 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) and 1 more.

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 545 (Connective Tissue Disorders with MCC, relative weight 2.3892), DRG 546 (Connective Tissue Disorders with CC, relative weight 1.1745) and DRG 547 (Connective Tissue Disorders without CC/MCC, relative weight 0.7526), in MDC 08 (Diseases and Disorders of the Musculoskeletal System and Connective Tissue), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 710.9 (unspecified diffuse connective tissue disease).