Microstomia

This code describes microstomia, a congenital or acquired condition characterized by an abnormally small oral opening. This restricted mouth aperture can significantly impair oral functions such as eating, speaking, and maintaining oral hygiene. It may result from various underlying etiologies, including genetic syndromes, scleroderma, burns, or surgical scarring.

Use this code when documentation clearly indicates a diagnosis of microstomia, regardless of its underlying cause. This diagnosis is often supported by physical examination findings noting a reduced interincisal distance or limited oral commissure opening. It is frequently encountered in patients with systemic sclerosis, certain craniofacial anomalies, or following extensive facial trauma or surgery.

• Always code the underlying cause of microstomia, if known and documented, in addition to this code.
• Differentiate from trismus (R25.2), which is a temporary or sustained spasm of the masticatory muscles, rather than a structural narrowing of the oral opening.
• Consider additional codes for associated conditions or complications, such as malnutrition (E40-E46) or dental issues (K00-K14), if documented.