Clinodactyly: Curving of the fifth finger (the little finger) toward the fourth finger (the ring finger). Sometimes called "fifth finger clinodactyly" to distinguish it from similar curving of other finger or toes.

Clinodactyly is a minor congenital malformation (birth defect). The basis for the clinodactyly is that the middle bone in the fifth finger is underdeveloped and, instead of being rectangular, is wedge- shaped.

Clinodactyly may occur as an isolated finding in a person who is entirely normal or it may be found in association with other congenital malformations and, sometimes, mental retardation. It is a common component of Down (trisomy 21) syndrome and Klinefelter (XXY) syndrome. No treatment is required for clinodactyly.

"Clinodactyly" is derived from the Greek "klinein" (to bend, slope or incline) and "dactylos" (finger, toe). Other English words formed from "klinein" include "clinocephaly" (a condition that causes skull depression or flatness) and "clinophobia" (fear of going to bed--that is, to bend the head to a pillow.) Other English words formed from "dactylos" include "dactylogram" (fingerprint) and "dactylography" (the study of fingerprints).