Bifid distal phalanx of the thumb

What it means

Partial duplication of the distal phalanx of the thumb. Depending on the severity, the appearance on x-ray can vary from a notched phalanx (the duplicated bone is almost completely fused with the phalanx) to a partially fused appearance of the two bones.

Note that with bifid distal phalanx, the terminal phalanx of the thumb is clefted but is still one bone. With duplication of the terminal phalanx of the thumb, the distal phalanx is split into two bones that are located side by side. With triphalangeal thumb, the thumb has three phalanxes located one after the other.

Rare diseases that can present with this4

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: Bifid distal phalanx of thumb · Bifid terminal phalanges of thumbs · Bifid thumb distal phalanx · Incipient distal thumb phalanx duplication · Notched outermost bone of thumb · Notched terminal thumb phalanx