M26.05 identifies macrogenia — abnormal enlargement of the chin (the bony symphyseal region of the mandible) classified as a major anomaly of jaw size under the dentofacial anomalies block.

Documentation tips

What should appear in the chart to support M26.05.

Source · Editorial brief grounded in 5 cited references ↓

• Document macrogenia explicitly by name; 'large chin' or 'chin prominence' alone may not map cleanly to M26.05 without a clinical diagnosis statement.
• Distinguish macrogenia (localized chin overgrowth at the symphysis) from mandibular hyperplasia (M26.03, global mandibular overgrowth) — the distinction must be clear in the operative or clinic note.
• Record imaging findings (cephalometric radiograph, CT, panoramic radiograph) that confirm skeletal enlargement of the chin region and support the diagnosis.
• If acromegaly or Robin's syndrome is present, document it separately and do not assign M26.05 — the Type 1 Excludes at M26.0 prohibits dual use in those scenarios.
• When macrogenia is treated concurrently with malocclusion or jaw-cranial base anomalies, document each condition independently so all relevant codes can be assigned.

Related CPT procedures

Procedure codes commonly billed with M26.05. 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 M26.05 and adjacent codes.

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

• Assigning M26.05 when the documented diagnosis is mandibular hyperplasia (M26.03) — macrogenia refers specifically to chin enlargement, not generalized mandibular overgrowth.
• Missing the Type 1 Excludes note at M26.0: if acromegaly (E22.0) is the underlying cause, M26.05 is excluded and E22.0 should drive the claim.
• Using the nonbillable parent code M26.0 (unspecified anomaly of jaw size) instead of the specific M26.05 — payers will reject or downcode non-billable headers.
• Failing to add a secondary code for any concurrent dentofacial functional abnormality (M26.5x) or malocclusion (M26.2x) when both are documented and treated, leaving reimbursable diagnoses uncaptured.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

Sibling codes

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