ICD-10-CM · Other

M26.01

Abnormal overgrowth of the maxillary bone resulting in a disproportionately large upper jaw relative to the mandible or cranial base.

Verified May 8, 2026 · 4 sources ↓

Status: Billable
Chapter: 13
Related CPT: 19
Region: Other

Drawn from CDCICD10DataAAPCFindacode

Documentation tips

What should appear in the chart to support M26.01.

Source · Editorial brief grounded in 4 cited references ↓

Specify 'maxillary hyperplasia' explicitly in the diagnosis — vague terms like 'jaw overgrowth' or 'prognathism' will not map cleanly to M26.01 and risk downcoding to M26.00 (unspecified).
Document whether the condition is congenital or acquired; both map to M26.01, but noting etiology strengthens the record for payer review.
Record imaging findings that support skeletal overgrowth — cephalometric analysis, CBCT measurements, or panoramic radiograph findings showing maxillary excess.
If alveolar bone overgrowth is the primary finding rather than the maxillary base, document that distinction clearly so the coder can route to M26.71 (alveolar maxillary hyperplasia) instead.
Rule out acromegaly in the chart before assigning M26.01; if endocrine workup was performed, note the result to justify using the M-code rather than E22.0.

Related CPT procedures

Procedure codes commonly billed with M26.01. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

21045 $1,061.15

Surgical removal or resection of the mandible involving extensive bone and soft tissue work, typically indicated for aggressive tumors, severe infection, or significant traumatic defect requiring wide-field operative exposure.

21046 $899.49

Excision of a benign tumor or cyst of the mandible requiring an intra-oral osteotomy, used for locally aggressive or destructive lesions that cannot be managed by simple enucleation or curettage alone.

21047 $1,076.51

Excision of a benign cyst or tumor of the mandible (lower jaw) using an extraoral approach with osteotomy and partial mandibulectomy, including repair.

21048 $906.83

Surgical removal of a benign cyst or tumor from the maxilla (upper jaw) via an intraoral approach that requires cutting through bone (osteotomy) — used for locally aggressive or destructive lesions.

21049 $1,021.07

Excision of a benign tumor or cyst of the maxilla requiring extra-oral osteotomy and partial maxillectomy — used for locally aggressive or destructive lesions.

21141 $1,208.44

Midface reconstruction via LeFort I osteotomy, single-piece maxillary segment moved in any direction, performed without bone graft.

21142 $1,238.17

LeFort I midface reconstruction performed in two separate maxillary segments, repositioning the upper jaw in any direction, without bone grafting.

21143 $1,273.58

LeFort I osteotomy of the maxilla performed in three or more bone segments, without bone grafting, for midface reconstruction.

21145 $1,390.81

LeFort I single-piece maxillary osteotomy performed with bone grafting to reposition the upper jaw and correct midface skeletal deformity.

21146 $1,452.94

LeFort I midface reconstruction split into two segments, moved in any direction, with bone grafts obtained at the same operative session — the classic approach for ungrafted unilateral alveolar clefts.

21147 $1,525.42

LeFort I osteotomy with segmentation into three or more pieces, repositioned in any direction, with bone grafting including autograft harvest

21150 $1,415.20

Reconstruction of the midface via a modified Le Fort II osteotomy pattern that advances the nasal-orbital complex anteriorly without mobilizing the zygoma.

21151 $1,553.81

Midface reconstruction via LeFort II osteotomy, movement in any direction, with bone grafting including autograft harvest

21154 $1,673.72

Extracranial LeFort III midface reconstruction requiring bone grafts, performed without a simultaneous LeFort I osteotomy.

21155 $1,851.41

Reconstruction of the midface using a modified LeFort III osteotomy with internal fixation, repositioning the midface skeleton to correct severe craniofacial deformities.

21160 $2,392.84

Reconstruction of the midface (Le Fort III level) with advancement using an internal distraction device — a high-complexity craniofacial procedure performed for severe midface hypoplasia or retrusion.

21199 $906.17

Segmental mandibular osteotomy with genioglossus muscle advancement — the lower jaw is cut in segments, repositioned, and the tongue-base muscle attachment is advanced forward.

70486 View procedure details

70487 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M26.01 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

Using M26.01 when alveolar maxillary hyperplasia (M26.71) is the correct site — the maxillary base and the alveolar process are distinct anatomical structures with separate codes.
Assigning M26.01 in the presence of a documented acromegaly diagnosis — Excludes1 at the M26.0 level prohibits this combination; E22.0 must be used instead.
Dropping to the unspecified parent M26.00 when the provider clearly documented 'maxillary hyperplasia' — specificity is available and should be captured.
Confusing maxillary hyperplasia (M26.01) with mandibular hyperplasia (M26.03) — verify which jaw is documented before assigning either code.

Clinical context

Source · Editorial summary grounded in 4 cited references ↓

M26.01 codes maxillary hyperplasia — a skeletal jaw size anomaly characterized by excessive bone growth of the maxilla. It sits under parent code M26.0 (Major anomalies of jaw size) within the M26 dentofacial anomalies block. Use it when the provider has specifically documented maxillary hyperplasia, hyperplasia of the maxillary bone, or congenital maxillary hyperplasia. Do not use it for alveolar maxillary hyperplasia, which has its own distinct code: M26.71.

This code applies in both surgical and non-surgical clinical settings — orthodontic evaluation, oral and maxillofacial surgery workup, orthognathic surgery planning, and hospital encounters. It maps to MS-DRG groupings 011–013 (tracheostomy for face/mouth/neck diagnoses) and 157–159 (dental and oral diseases) depending on complication/comorbidity level, so accurate specificity affects DRG assignment.

Two critical Excludes1 conditions block M26.0x codes entirely: acromegaly (E22.0) and Robin's syndrome (Q87.0). If either of those is the documented etiology, do not assign M26.01 — assign the underlying condition code instead. Acromegaly-driven jaw overgrowth is classified under the endocrine disorder, not the musculoskeletal anomaly.

Sibling codes

Other billable codes under M26.0 (laterality / anatomic variants).

M26.00

Unspecified anomaly of jaw size

M26.06

Microgenia

M26.03

Mandibular hyperplasia

M26.04

Mandibular hypoplasia

M26.07

Excessive tuberosity of jaw

M26.09

Other specified anomalies of jaw size

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 4 cited references ↓

01What is the difference between M26.01 and M26.71?

M26.01 codes hyperplasia of the maxillary bone (skeletal base), while M26.71 codes alveolar maxillary hyperplasia (the tooth-bearing alveolar process). The distinction depends on which anatomical structure the provider documents as overgrown.

02Can M26.01 be used for a patient with acromegaly who also has jaw overgrowth?

No. The Excludes1 annotation at M26.0 prohibits assigning any M26.0x code when acromegaly (E22.0) is the documented diagnosis. The jaw overgrowth in acromegaly is coded under E22.0.

03Is M26.01 appropriate for congenital maxillary hyperplasia?

Yes. 'Congenital maxillary hyperplasia' and 'hyperplasia of maxillary bone' are both listed as approximate synonyms for M26.01 in the ICD-10-CM index. The code covers both congenital and non-congenital presentations.

04Does M26.01 require a 7th-character extension?

No. M26.01 is a 5-character M-code and does not use 7th-character extensions. 7th characters (A, D, S) apply to injury S-codes, not musculoskeletal anomaly M-codes.

05What CPT codes commonly pair with M26.01 on orthognathic surgery claims?

Le Fort osteotomy codes (21141–21160, 21199) are the most frequent surgical pairings. Imaging support codes like 70486 (CT maxillofacial without contrast) and 70487 (with contrast) also appear on pre-operative workup claims.

06Should M26.01 be listed as the primary diagnosis on an orthognathic surgery claim?

List the diagnosis that is chiefly responsible for the encounter first. If maxillary hyperplasia is the indication driving the surgical procedure, M26.01 is the appropriate primary diagnosis. Concurrent malocclusion codes (M26.2x) are reported as additional diagnoses when documented.

07Is M26.01 ever used with Robin's syndrome (Q87.0)?

No. Robin's syndrome is an Excludes1 condition at the M26.0 parent level. If Robin's syndrome is documented, assign Q87.0 — not M26.01 or any other M26.0x code.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

01CDC ICD-10-CM Tabular List 2026 (effective October 1, 2025)
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M26-M27/M26-/M26.01
03
aapc.com
https://www.aapc.com/codes/icd-10-codes/M26.01
04
findacode.com
https://www.findacode.com/icd-10-cm/icd-10-cm-diagnosis-codes-M26-group.html

Mira AI Scribe

Mira's AI scribe captures the provider's explicit lateralized jaw diagnosis ('maxillary hyperplasia'), associated imaging data (cephalometric measurements, CBCT findings, Angle classification if concurrent malocclusion is noted), and any notation ruling out acromegaly or Robin's syndrome. This prevents fallback to the unspecified M26.00, avoids an Excludes1 conflict with E22.0, and ensures the correct M26.01 vs. M26.71 split is made before the claim is submitted.

See how Mira captures M26.01 documentation