Overgrowth of the mandible (lower jaw) classified as a major anomaly of jaw size, reported under the dentofacial anomalies section of ICD-10-CM.

Documentation tips

What should appear in the chart to support M26.03.

Source · Editorial brief grounded in 6 cited references ↓

• Specify the mandible by name — 'lower jaw hyperplasia' alone may prompt a query; documentation should read 'mandibular hyperplasia' or name the affected structure (condyle, coronoid process, body).
• Document whether the hyperplasia is congenital or acquired/active condylar hyperplasia, as this distinction drives surgical planning and supports medical necessity.
• Record imaging findings (panoramic radiograph, CBCT, or MRI) that confirm mandibular overgrowth — bone scintigraphy results indicating active condylar growth are particularly valuable for prior authorization.
• If asymmetry is present, note laterality of the dominant condylar hyperplasia (right vs. left) in the operative note even though M26.03 itself has no laterality subcode.
• Exclude acromegaly (E22.0) and Robin's syndrome (Q87.0) in the assessment; if either is present, M26.03 is not reportable per Excludes1 rules at the M26.0 level.
• Distinguish basal mandibular hyperplasia from alveolar mandibular hyperplasia — if overgrowth is confined to the alveolar process, M26.72 applies instead of M26.03.

Related CPT procedures

Procedure codes commonly billed with M26.03. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

Common coding pitfalls

The recurring mistakes coders make with M26.03 and adjacent codes.

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

• Using M26.03 when acromegaly (E22.0) is the documented etiology — Excludes1 at the M26.0 level prohibits this combination; code only E22.0.
• Confusing M26.03 (basal/condylar mandibular hyperplasia) with M26.72 (alveolar mandibular hyperplasia) — the alveolar process has its own distinct code and the two are not interchangeable.
• Defaulting to M26.09 (other specified anomalies of jaw size) when the mandible is clearly documented as hyperplastic — M26.03 is the specific, billable code and should be used over the catch-all.
• Coding M26.03 for Robin's syndrome-related micrognathia/retrognathia — Robin's syndrome is excluded at the parent level (Q87.0 applies instead).
• Omitting a secondary malocclusion code (M26.2x series) when the mandibular hyperplasia has produced a documented Angle Class III or open-bite relationship — these are separately reportable and support functional medical necessity.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

Sibling codes

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