Macrostomia

Macrostomia is a congenital anomaly characterized by an abnormally large mouth opening, often extending towards the ears. This condition results from incomplete fusion of the maxillary and mandibular prominences during embryonic development, leading to a widened oral fissure. It can occur unilaterally or bilaterally and may be associated with other craniofacial abnormalities.

This code is used when documentation clearly indicates a diagnosis of macrostomia, whether isolated or as part of a syndrome. It is appropriate for congenital cases identified at birth or during early childhood. Supporting documentation should include physician notes detailing the physical examination findings of an enlarged oral aperture.

• Differentiate from microstomia (Q18.5), which is an abnormally small mouth opening.
• Be sure to code any associated congenital anomalies or syndromes separately, if documented.
• Confirm laterality (unilateral vs. bilateral) if specified in the medical record, though this code does not differentiate.