Thumb symphalangism

What it means

Congenital fusion (ankylosis) of the interphalangeal joint of the thumb.

Symphalangism is caused by a failure of segmentation that occurs during early fetal development.

Rare diseases that can present with this1

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: Fused thumb phalanges · Symphalangism of the distal and proximal phalanges of the thumb