ICD-10-CM 2027 diagnosis code
I00Rheumatic fever without heart involvement
I00 is a valid, billable ICD-10-CM code for rheumatic fever without heart involvement. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.
Looking up by condition? See ICD-10 code for Rheumatic fever.
Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About I00
I00 is the ICD-10-CM diagnosis code for rheumatic fever without heart involvement. It belongs to block I00-I02 (acute rheumatic fever) and chapter 9 (diseases of the circulatory system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.
Don't report I00 together with the conditions in its Excludes1 note: rheumatic fever with heart involvement (I01.0-I01.9).
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 390 (rheumatic fever without mention of heart involvement).
Coding notes
Notes that apply from higher levels
Instructions written at a parent level also apply to I00.
Broader instructions also apply from Chapter 9: Diseases of the circulatory system.
Alphabetic index entries
5 entriesTerms in the official ICD-10-CM index that lead to I00.
- Erythema, erythematous (infectional) (inflammation) › marginatum › in (due to) acute rheumatic fever
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › rheumatic (active) (acute) (chronic) (subacute)
- Pneumonia (acute) (double) (migratory) (purulent) (septic) (unresolved) › in (due to) › rheumatic fever
- Pneumonia (acute) (double) (migratory) (purulent) (septic) (unresolved) › rheumatic
- Rheumatic (acute) (subacute) › pneumonia
Codes whose notes reference I00
MS-DRG v44.0 grouping
All DRGs →Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.
MDC 08 · Diseases and Disorders of the Musculoskeletal System and Connective Tissue
ICD-9-CM equivalent
Converter →- 390Rheumatic fever without mention of heart involvementexact
From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
- No changes since FY2016.
Common questions about I00
Is I00 billable?
- Yes. I00 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can I00 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict I00 as a principal diagnosis.
Is I00 a CC or MCC?
- No. I00 is neither a CC nor an MCC under MS-DRG v44.0.
What DRG does I00 group to?
- I00 is used in the MS-DRG v44.0 logic for MS-DRG 545 (Connective Tissue Disorders with MCC), MS-DRG 546 (Connective Tissue Disorders with CC) and MS-DRG 547 (Connective Tissue Disorders without CC/MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.
What is the ICD-9 code for I00?
- The CMS General Equivalence Mappings map I00 to ICD-9-CM 390.