M35.81 Multisystem inflammatory syndrome

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applicable to

• MIS-A
• MIS-C
• Multisystem inflammatory syndrome in adults
• Multisystem inflammatory syndrome in children
• Pediatric inflammatory multisystem syndrome
• PIMS

Code first

• , if applicable, COVID-19 (U07.1)

Use additional code

• code, if applicable, for:
• exposure to COVID-19 or SARS-CoV-2 infection (Z20.822)
• personal history of COVID-19 (Z86.16)
• post COVID-19 condition (U09.9)

Code also

• any associated complications such as:
• acute hepatic failure (K72.0-)
• acute kidney failure (N17.-)
• acute myocarditis (I40.-)
• acute respiratory distress syndrome (J80)
• cardiac arrhythmia (I47-I49.-)
• pneumonia due to COVID-19 (J12.82)
• severe sepsis (R65.2-)
• viral cardiomyopathy (B33.24)
• viral pericarditis (B33.23)

Applies from M35 Other systemic involvement of connective tissue

Excludes1 (never code together)

• reactive perforating collagenosis (L87.1)

Risk adjustment (HCC)

• CMS-HCC V28: HCC 2 — Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock
• CMS-HCC V22: HCC 2 — Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock
• ESRD V24: HCC 2

MS-DRG index

Defines the logic of DRG(s) 545-547 in MDC 08.

Code annotations containing back-references to M35.81

Back-references to M35.81

• Code First: U09.9 Post COVID-19 condition, unspecified ("multisystem inflammatory syndrome (M35.81)")

Back-references to M35

• Type 2 Excludes: I77 Other disorders of arteries and arterioles ("collagen (vascular) diseases (M30-M36)")
• Type 2 Excludes: J82 Pulmonary eosinophilia, not elsewhere classified ("pulmonary eosinophilia due to systemic connective tissue disorders (M30-M36)")
• Code First: J84.170 Interstitial lung disease with progressive fibrotic phenotype in diseases classified elsewhere ("systemic connective tissue disorders (M30-M36)")
• Type 1 Excludes: L94 Other localized connective tissue disorders ("systemic connective tissue disorders (M30-M36)")

Diagnosis Index entries for M35.81

• MIS-A
• MIS-C
• Multisystem inflammatory syndrome (in adult) (in children)
• Pediatric inflammatory multisystem syndrome
• PIMS
• Syndrome › multisystem inflammatory (in adults) (in children)
• Syndrome › pediatric inflammatory multisystem

Nearby codes

• M35.4 Diffuse (eosinophilic) fasciitis
• M35.5 Multifocal fibrosclerosis
• M35.6 Relapsing panniculitis [Weber-Christian]
• M35.7 Hypermobility syndrome
• M35.8 Other specified systemic involvement of connective tissue
• M35.81 Multisystem inflammatory syndrome (this code)
• M35.89 Other specified systemic involvement of connective tissue
• M35.9 Systemic involvement of connective tissue, unspecified