2026 ICD-10-CM Diagnosis Code I79.1Aortitis in diseases classified elsewhere
ICD-10-CM Codes›I00–I99›I70-I79›I79
- Billable — Valid for Submission
- Not Chronic
I79.1 is a billable ICD-10-CM diagnosis code for aortitis in diseases classified elsewhere. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 299 through 301. The code is a manifestation code that cannot be reported as the principal diagnosis. Coders also document this condition as immunoglobulin G4 related aortitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified circulatory disease.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for I79.1.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Immunoglobulin G4 related aortitis
- Immunoglobulin G4 related disease
- Immunoglobulin G4 related periaortitis
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Code First
- underlying disease
Type 1 Excludes
- syphilitic aortitis A52.02
Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first followed by the manifestation. Wherever such a combination exists, there is a "use additional code" note at the etiology code, and a "code first" note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Vascular Diseases
Your vascular system is your body's network of blood vessels. It includes your:
The full article covers:
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- What causes vascular diseases?
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- How are vascular diseases diagnosed?
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Read the full article at MedlinePlus
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Convert I79.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About I79.1Overview
Is I79.1 a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report aortitis in diseases classified elsewhere on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does I79.1 group to?
On inpatient claims, aortitis in diseases classified elsewhere maps to MS-DRG 299, 300, 301, with relative weights from 0.7197 to 1.6327 depending on complications. Higher weights mean higher Medicare reimbursement.
Can I79.1 be a principal diagnosis?
No. This is a manifestation code: aortitis in diseases classified elsewhere describes the manifestation of an underlying disease rather than the disease itself, so the underlying condition is sequenced first.
What is the ICD-9 equivalent of I79.1?
Under the General Equivalence Mappings, aortitis in diseases classified elsewhere converts to ICD-9-CM 443.81 (angiopathy in other dis). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
