Baby arm

A baby arm is a human deformity which renders an adult arm the size of a baby's. Usually present from birth, baby arm disorder most commonly affects the left arm. Contrary to early belief, baby arm is not contagious; it is however inheritable as a dominant gene. Baby arm sufferers generally lead normal and healthy lives, although their condition has made certain occupations which require the use of two normal-sized arms nearly unattainable. Several celebrities are afflicted with baby arm, including musicians Ivan Hrvatska and Pleasureman Gunther, former pro basketball player Cherokee Parks, Heat from I Love New York, and DJ Paul from Three 6 Mafia.

Fictional representations
Tom Robinson from To Kill a Mockingbird had post-natal baby arm resulting from having his arm caught in a cotton gin when he was a boy, and the book's success has been credited with raising awareness for the condition.

Nemo in Finding Nemo has one fin which is significantly smaller and weaker than the other, which is called his 'Lucky Fin'. His father is over-protective of Nemo in part because of his condition.

Prostheses
Synthetic attachments can be used post-amputation or malformation of limbs.