Narrow jaw

What it means

Bigonial distance (lower facial width) more than 2 standard deviations below the mean (objective); or an apparently decreased width of the lower jaw (mandible) when viewed from the front (subjective).

The width of the jaw is measured from the right gonion to the left gonion using spreading calipers. The gonion is the point at the angle of the bony mandible where the ramus changes direction to become the body of the mandible. It faces inferiorly and medially and is best found by placing a finger over the outward facing angle and rolling the finger downwards and inwards.

Rare diseases that can present with this2

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Narrow lower jaw · Narrow mandible · Thin lower face · Thin lower jaw