ICD-10 code M27.8: Other specified diseases of jaws

Key takeaways

M27.8 is a billable ICD-10-CM code for FY2026, effective October 1, 2025, covering other specified diseases of jaws.

The five named inclusions are cherubism, fibrous dysplasia of the jaw, oral exostosis, and unilateral condylar hyperplasia or hypoplasia.

Torus mandibularis and Stafne bone cyst code to M27.0, and central giant cell granuloma codes to M27.1.

Apply M27.8 only when no more specific M27 subcode fits, because unspecified coding is a common rejection trigger.

Practice management software like Pabau ties the named diagnosis to the claim, so the documentation holds up at audit.

ICD-10 code M27.8 is a billable ICD-10-CM code for other specified diseases of jaws. It is valid for FY2026, effective October 1, 2025.

Use it when the ICD-10-CM index sends a named jaw condition to M27.8. The inclusions are cherubism, fibrous dysplasia of the jaw, and oral exostosis. Unilateral condylar hyperplasia and unilateral condylar hypoplasia complete the list.

Torus mandibularis, Stafne bone cyst, and giant cell granuloma all sound like they belong here. Each one codes somewhere else, and the differential below shows where.

M27.8 at a glance

M27.8 is a billable, specific ICD-10-CM code valid for reimbursement in fiscal year 2026. The 2026 edition took effect on October 1, 2025, per CMS ICD-10-CM updates. Apply it when the clinical picture matches a named inclusion and no M27 sibling describes it more precisely.

Code classification and hierarchy

M27.8 sits in the musculoskeletal chapter rather than the dental chapter, so jaw pathology is indexed under M00-M99. The WHO ICD-10 framework underpins the American clinical modification, which CDC/NCHS and CMS maintain together.

• Chapter XIII (M00-M99): Diseases of the musculoskeletal system and connective tissue
• Block M26-M27: Dentofacial anomalies and other disorders of jaw
• Category M27: Other diseases of jaws (parent code, non-billable)
• Code M27.8: Other specified diseases of jaws (billable, FY2026)

The “other specified” designation is deliberate. ICD-10-CM uses it for conditions that the index names but does not give a dedicated subcode within M27. Congenital anomalies of the mouth sit outside M27 altogether, as Q18.5 shows.

What does M27.8 cover?

The ICD-10-CM tabular list names five conditions under M27.8. Each is a distinct jaw pathology with no more specific home in the M27 family. The CDC/NCHS ICD-10-CM tool confirms which conditions map here for the current fiscal year.

Cherubism and fibrous dysplasia of the jaw

Cherubism is a rare autosomal dominant condition. It replaces jaw bone with fibrous tissue on both sides during childhood, producing the characteristic full-cheeked appearance. The tabular list names it as an inclusion under M27.8.

Fibrous dysplasia of the jaw replaces normal bone with fibrous tissue, which expands the mandible or maxilla. It is a named inclusion under M27.8. Fibrous dysplasia at several skeletal sites codes to Q78.1, so the record needs to say which one you mean.

Oral exostosis and condylar asymmetry

Three further inclusions cover the shape of the jaw bone itself. Documentation has to name the exact lesion, because that is what ties the claim to the index entry.

• Oral exostosis, or exostosis of jaw: A bony outgrowth of the maxilla or mandible. Its ICD-9-CM predecessor code was 526.81, which appears in the crosswalk below.
• Unilateral condylar hyperplasia: Asymmetric overgrowth of one mandibular condyle. It is a named inclusion under M27.8, and it drives many facial asymmetry referrals.
• Unilateral condylar hypoplasia: Underdevelopment of one mandibular condyle, which shortens that side of the mandible. It shares the M27.8 inclusion list with hyperplasia, so the note has to record which one you found.

Conditions that look similar but code elsewhere

Five jaw conditions are routinely filed against M27.8 by habit. The index puts each of them somewhere else, so check this table before you submit.

The pathology report decides the giant cell entry. Central lesions are M27.1 and peripheral lesions are K06.8, so read the variant before you pick a code.

Documentation that supports the code

M27.8 is an “other specified” code, so the record has to name the specific condition. Wording such as “jaw lesion” or “jaw abnormality” points at the unspecified code M27.9 instead, which invites payer scrutiny. Working from current patient records is what keeps that specificity available months later.

Payers expect the named diagnosis, imaging from a panoramic X-ray, CBCT, or MRI, and histopathology where the lesion type is in question. For a developmental lesion such as cherubism, family history and genetic findings strengthen the record. Good medical forms at intake set up defensible coding downstream.

Structured patient records hold imaging results, operative findings, and diagnosis narratives in one searchable place. Practices that capture the diagnosis on digital clinical forms at the point of care also cut transcription errors before billing sees the code.

Record retention rules decide how long that evidence stays reachable, and they vary by state. A jaw lesion documented in 2020 can still be audited, so retention is part of the coding question.

Which specialties file this code?

Oral and maxillofacial surgery files M27.8 most often, with dentistry, ENT, and radiology close behind. Each of them meets jaw pathology in a different setting, and code reference pages rarely say who submits it.

• Oral and maxillofacial surgeons: The primary users. Fibrous dysplasia, condylar hyperplasia, and jaw exostosis are all operative conditions here, and M27.8 appears on pre-authorization requests and post-operative claims.
• General dentists and prosthodontists: They meet bony overgrowths during prosthetic work-up, then refer for removal or monitor. Torus mandibularis found this way codes to M27.0.
• ENT (otolaryngology): Jaw lesions that affect the airway or present as facial asymmetry are often evaluated here first, before onward referral.
• Radiologists: Incidental jaw findings on CBCT, a panoramic X-ray, or MRI generate the diagnosis code that the practice then carries onto the claim.
• Plastic and reconstructive teams: Facial reconstruction after lesion excision runs through plastic surgery EMR workflows, where M27.8 sits as a secondary diagnosis.
• Regenerative medicine teams: Bone grafting after jaw lesion removal is charted in regenerative medicine EMR workflows against the same diagnosis code.

Related codes in the M27 category

M27.8 applies only when no more specific sibling describes the diagnosis. Selecting the sibling first is the whole job, and the table below maps the family.

Choosing between M27.8 and its siblings

Check each sibling before defaulting to M27.8. The five comparisons below cover almost every jaw claim.

• M27.8 vs. M27.0: M27.0 covers developmental disorders of jaws. Torus mandibularis, torus palatinus, and Stafne’s cyst all belong there.
• M27.8 vs. M27.1: M27.1 is central giant cell granuloma. When pathology confirms that lesion, M27.1 is the code regardless of any synonym overlap.
• M27.8 vs. M27.2: M27.2 covers inflammatory jaw conditions such as osteitis and periostitis. Fibrous dysplasia is not inflammatory, so it stays at M27.8.
• M27.8 vs. M27.4x: Jaw cysts have their own subcodes, from M27.40 to M27.49. A dentigerous cyst never codes to M27.8.
• M27.8 vs. M27.9: M27.9 is for a jaw disease that genuinely cannot be identified. Coding M27.9 when the chart names an M27.8 inclusion is an error.

ICD-9-CM to ICD-10-CM crosswalk

Retroactive audits and pre-2015 records still reference ICD-9 codes. The mapping below follows the General Equivalence Mapping (GEM) files, and those mappings are approximate and sometimes one-to-many. Verify against current GEM files via the AAPC ICD-10-CM lookup before quoting one in a formal response.

The distinction matters in practice. An audit requesting pre-2015 records will reference ICD-9 codes, and the crosswalk lets a coder explain clinical continuity without conflating the two systems. A routine medical chart audit is usually where those legacy references surface.

Coding tips and common errors

Most M27.8 claim problems come from vague documentation that cannot support the code at audit. The rest come from reaching for M27.8 when a specific sibling exists, or from pairing it with a procedure code that does not match.

• Name the condition in the chart. “Other specified disease of jaw” is not a diagnosis. The chart must name the condition, such as cherubism or fibrous dysplasia of the mandible.
• Avoid M27.9 when a named condition is documented. Unspecified codes attract payer scrutiny. Where the index confirms an inclusion, M27.8 is the stronger submission.
• Check for a more specific subcode first. Central giant cell granuloma, jaw cysts, and implant failures all have their own subcodes. M27.8 is the residual code for named conditions the index sends there.
• Laterality is not part of M27.8. The code carries no laterality extension. Record the side in the narrative and stop hunting for a digit that does not exist.
• Pair M27.8 with a procedure code that matches. Excision of a benign jaw tumor or cyst bills from the 21040 to 21048 range. Facial skeleton reconstruction sits in a different family, such as CPT code 21154. A mismatch is a common edit trigger.
• Verify each fiscal year. The code set updates every October 1. Inclusions are added and moved, so confirm M27.8 still holds at the start of each fiscal year.

How Pabau keeps jaw diagnoses claim-ready

In many practices the diagnosis lives in the operative note, the imaging sits in a separate viewer, and the claim gets built later from memory. When a payer asks why M27.8 was submitted, somebody has to reassemble the story from three systems.

Practice management software like Pabau keeps those pieces on one patient record. The named jaw condition, the CBCT report, the consent, and the invoice all hang off the same timeline. Your coder reads the chart instead of chasing it.

Pabau’s claims management software then tracks what each payer did with the claim. Rejections show up as a pattern you can act on, rather than a write-off you find at month end.

Stop losing jaw claims to thin documentation

Pabau helps oral surgery and maxillofacial practices submit M27.8 with a complete documentation trail. Fewer payer rejections mean fewer write-offs at month end.

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Conclusion

M27.8 is a narrow code with a wide reputation. It carries five named inclusions, and several of the conditions most often filed against it belong to M27.0, M27.1, or M27.4x.

Most of the work happens in the chart. Name the lesion, attach the imaging, and run the index query before you submit. Do that and the code stops being a judgment call.

Practice management software that keeps documentation and claims in one place makes that routine rather than a scramble. Book a demo to see how Pabau handles diagnosis documentation and claim tracking for oral surgery practices.

Continue your research

Coding an excision of a jaw lesion? CPT code 21048 covers the billing detail for a benign tumor or cyst of the maxilla.

Repairing facial nerve damage after jaw surgery? CPT code 15845 sets out how the graft is documented and billed.

Sending records with a jaw surgery referral? Dental records release form gives you a compliant release to attach.

Onboarding a new oral surgery patient? Dental new patient form captures the history and consent your first appointment needs.

Clearing a patient before an operative date? Dental clearance form documents the physician sign-off you need on file.

Frequently asked questions