M04.9Autoinflammatory syndrome, unspecified

M04.9 is the ICD-10-CM diagnosis code for autoinflammatory syndrome, unspecified. It belongs to category M04 (autoinflammatory syndromes), block M04 (autoinflammatory syndromes) 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 M04, choose M04.9 (Autoinflammatory syndrome, unspecified) only when documentation doesn't support a more specific option: periodic fever syndromes (M04.1), Cryopyrin-associated periodic syndromes (M04.2), VEXAS syndrome (M04.3) and other autoinflammatory syndromes (M04.8).

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 was added in FY2017, effective October 1, 2016.

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