Heart-hand syndrome type 2 is an extremely rare heart-hand syndrome (see this term) described in two families to date, that is characterized by upper limb malformations (brachytelephalangy type D, hypoplastic deltoids, mild shortening of the fourth and fifth metacarpals in some individuals, skeletal anomalies in the humerus, radius, ulnae, and thenar bones) and cardiac arrhythmias (junctional rhythms and atrial fibrillation).

A thumb with three phalanges in a single, proximo-distal axis. Thus, this term applies if the thumb has an accessory phalanx, leading to a digit like appearance of the thumb.