Proboscis (anomaly)

In teratology, a proboscis is a blind-ended, tube-like structure, commonly located in the middle of the face.

It is commonly seen in severe forms of holoprosencephaly that include cyclopia and is usually the result of abnormal development of the nose.

A holoprosencephalic proboscis is found in holoprosencephaly (a condition in which the forebrain of the embryo fails to develop into two hemispheres as it should).

In cebocephaly, no proboscis formation occurs, but a single-nostril nose is present.

A disruptive proboscis occurs if an hamartoneoplastic lesion (benign growths such as are found in disorders like neofibromatosis and tubular sclerosis) arises in the prosencephalon (forebrain) of the embryo in its early stages of development.

Proboscis in Patau syndrome . Cyclopia (a single median eye) is associated with arrhinia (absence of the nose) and proboscis formation above the eye.