2026 ICD-10-CM Diagnosis Code M46.91Unspecified inflammatory spondylopathy, occipito-atlanto-axial region
ICD-10-CM Codes›M00–M99›M45-M49›M46
- Billable — Valid for Submission
- Not Chronic
M46.91 is a billable ICD-10-CM diagnosis code for unspecified inflammatory spondylopathy, occipito-atlanto-axial region. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 551 through 552. Coders also document this condition as axial spondyloarthritis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Spondylopathies/spondyloarthropathy (including infective).
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Axial spondyloarthritis
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
- Spondylopathy - M48.9
- inflammatory - M46.90
- occipito-atlanto-axial region - M46.91
External Cause of Injuries IndexGuidance
References for this code in the External Cause of Injuries Index.
- Spondylopathy
- inflammatory
- occipito-atlanto-axial region
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Axial Spondyloarthritis
a spectrum of chronic inflammatory conditions affecting the axial joints (e.g., spine), characterized by pain, stiffness of joints (ankylosis), reduced mobility and inflammation. when joint inflammation and damage are visible on regular x-rays it is called ankylosing spondylitis; otherwise it is referred to as non-radiographic axial spondyloarthritis. hla-b27 antigen is a biomarker and il-23/il-17 pathway a potential therapeutic target for axial and other related spondyloarthritis.Non-Radiographic Axial Spondyloarthritis
chronic inflammatory conditions affecting the axial joints which cannot be detectable on x-rays. it is characterized by pain, stiffness of joints and inflammation. non-radiographic axial spondyloarthritis can have symptoms onset before the age of 45 and progress to more severe ankylosing spondylitis over time.
Patient EducationClinical
Spine Injuries and Disorders
Your backbone, or spine, is made up of 26 bone discs called vertebrae. The vertebrae protect your spinal cord and allow you to stand and bend. A number of problems can change the structure of the spine or damage the vertebrae and surrounding tissue. They include:
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Convert M46.91 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About M46.91Overview
Is M46.91 (Unspecified inflammatory spondylopathy) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report unspecified inflammatory spondylopathy, occipito-atlanto-axial region on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does M46.91 group to?
When unspecified inflammatory spondylopathy, occipito-atlanto-axial region is the principal diagnosis on an inpatient stay, it groups to MS-DRG 551, 552, with relative weights from 0.9613 to 1.6761 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of M46.91?
Under the General Equivalence Mappings, unspecified inflammatory spondylopathy, occipito-atlanto-axial region converts to ICD-9-CM 720.9 (inflam spondylopathy NOS). 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.
