Adactylia, unilateral is a rare congenital condition affecting the hand. People with this condition are born with a partially formed hand where the terminal portions of digits 2 to 5 are absent. The thumbs in these individuals may be mildly underdeveloped and there may be small nail remnants on the shortened digits. Some of the hand bones, particularly the metacarpal bones, may also be variably reduced in size. This condition does not usually come with other syndromic features, meaning that it typically affects only the hand. It is considered a non-syndromic terminal transverse limb reduction defect, which means that the limb difference is isolated and not part of a broader syndrome affecting other parts of the body.

The main physical findings in adactylia, unilateral include the absence of the terminal portions of digits 2 to 5 on one hand. Additionally, a mildly underdeveloped thumb and small nail remnants on the digit stumps are observed. There can also be a reduction in the size of some hand bones, such as the metacarpal bones.

Adactylia, unilateral is a congenital condition, meaning it is present at birth. The exact cause is not fully understood and there are no identified genetic mutations linked to this condition, as noted by the absence of known genes associated with it.