Cyclopia
Encyclopedia
Cyclopia is a rare form of holoprosencephaly
and is a congenital disorder
(birth defect) characterized by the failure of the embryonic prosencephalon
to properly divide the orbits
of the eye into two cavities. Its incidence is 1 in 16,000 in born animals, and 1 in 250 in embryos, one in 2,500 that end in miscarriage.
. Such a proboscis generally appears above the central eye, or on the back, and is characteristic of a form of cyclopia called rhinencephaly or rhinocephaly. Most such embryos are either naturally aborted
or are stillborn
upon delivery
/ hatching.
Although cyclopia is rare, several cyclopic human babies are preserved in medical museums (e.g. The Vrolik Museum, Amsterdam).
Some extreme cases of cyclopia have been documented in inbred farm animals (horses, sheep, pigs, and sometimes chickens). In such cases, the nose and mouth fail to form, or the nose grows from the roof of the mouth obstructing airflow, resulting in suffocation shortly after birth.
or 2-deoxyjervine, found in the plant Veratrum californicum
(also known as corn lily or false hellebore). The mistake of ingesting Veratrum californicum while pregnant is often because hellebore
, a plant with which it is easily confused, is recommended as a natural treatment for vomiting
, cramp
s, and poor circulation, three conditions that are quite common in pregnant
women. Cyclopia can occur in the womb when certain proteins are inappropriately expressed and causes the brain to stay a whole instead of having two distinct hemispheres, which also means one optic lobe and one olfactory lobe resulting in one eye.
Shh
(Sonic Hedgehog Gene Regulator, named after the effects a mutation in the gene had on the forming embryo of fruit flies studied by scientists; a spiky appearance under a microscope, similar to that of its video game character namesake
) is involved in the separation of the single eye field into two bilateral fields. Although not proven, it is thought that shh emitted from the prechordal plate suppresses Pax6
which causes the eye field to divide into two. If the shh gene is mutated, the result is cyclopia, a single eye in the center of the face (Gilbert, 2000).
apparently suffering from cyclopia reads:
On December 28, 2005, a kitten with cyclopia, "Cy", was born in the Redmond
, Oregon
, United States
and died about one day after birth.
Holoprosencephaly
Holoprosencephaly is a cephalic disorder in which the prosencephalon fails to develop into two hemispheres. Normally, the forebrain is formed and the face begins to develop in the fifth and sixth weeks of human pregnancy...
and is a congenital disorder
Congenital disorder
A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...
(birth defect) characterized by the failure of the embryonic prosencephalon
Prosencephalon
In the anatomy of the brain of vertebrates, the prosencephalon is the rostral-most portion of the brain. The prosencephalon, the mesencephalon , and rhombencephalon are the three primary portions of the brain during early development of the central nervous system...
to properly divide the orbits
Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...
of the eye into two cavities. Its incidence is 1 in 16,000 in born animals, and 1 in 250 in embryos, one in 2,500 that end in miscarriage.
Presentation
Typically, the face is either missing or replaced with a non-functioning nose in the form of a proboscisProboscis
A proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In simpler terms, a proboscis is the straw-like mouth found in several varieties of species.-Etymology:...
. Such a proboscis generally appears above the central eye, or on the back, and is characteristic of a form of cyclopia called rhinencephaly or rhinocephaly. Most such embryos are either naturally aborted
Miscarriage
Miscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving independently, generally defined in humans at prior to 20 weeks of gestation...
or are stillborn
Stillbirth
A stillbirth occurs when a fetus has died in the uterus. The Australian definition specifies that fetal death is termed a stillbirth after 20 weeks gestation or the fetus weighs more than . Once the fetus has died the mother still has contractions and remains undelivered. The term is often used in...
upon delivery
Childbirth
Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...
/ hatching.
Although cyclopia is rare, several cyclopic human babies are preserved in medical museums (e.g. The Vrolik Museum, Amsterdam).
Some extreme cases of cyclopia have been documented in inbred farm animals (horses, sheep, pigs, and sometimes chickens). In such cases, the nose and mouth fail to form, or the nose grows from the roof of the mouth obstructing airflow, resulting in suffocation shortly after birth.
Causes
Genetic problems or toxins can cause problems in the embryonic forebrain-dividing process. One highly teratogenic alkaloid toxin that can cause cyclopia is cyclopamineCyclopamine
Cyclopamine is a naturally occurring chemical that belongs to the group of steroidal jerveratrum alkaloids. It is a teratogen isolated from the corn lily that causes usually fatal birth defects. It can prevent the fetal brain from dividing into two lobes and cause the development of a single eye...
or 2-deoxyjervine, found in the plant Veratrum californicum
Veratrum californicum
Veratrum californicum is a poisonous plant native to mountain meadows at 3500 to 11,000ft elevation in southwestern North America, the Sierra Nevada and Rocky Mountains, and as far north as Washington State. It grows 1 to 2 meters tall, with an erect, unbranched, heavily leafy stem resembling a...
(also known as corn lily or false hellebore). The mistake of ingesting Veratrum californicum while pregnant is often because hellebore
Hellebore
Commonly known as hellebores, members of the genus Helleborus comprise approximately 20 species of herbaceous perennial flowering plants in the family Ranunculaceae, within which it gave its name to the tribe of Helleboreae...
, a plant with which it is easily confused, is recommended as a natural treatment for vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, cramp
Cramp
Cramps are unpleasant, often painful sensations caused by muscle contraction or over shortening. Common causes of skeletal muscle cramps include muscle fatigue, low sodium, and low potassium...
s, and poor circulation, three conditions that are quite common in pregnant
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
women. Cyclopia can occur in the womb when certain proteins are inappropriately expressed and causes the brain to stay a whole instead of having two distinct hemispheres, which also means one optic lobe and one olfactory lobe resulting in one eye.
Shh
Sonic hedgehog
Sonic hedgehog homolog is one of three proteins in the mammalian signaling pathway family called hedgehog, the others being desert hedgehog and Indian hedgehog . SHH is the best studied ligand of the hedgehog signaling pathway. It plays a key role in regulating vertebrate organogenesis, such as...
(Sonic Hedgehog Gene Regulator, named after the effects a mutation in the gene had on the forming embryo of fruit flies studied by scientists; a spiky appearance under a microscope, similar to that of its video game character namesake
Sonic the Hedgehog (character)
, trademarked Sonic The Hedgehog, is a video game character and the main protagonist of the Sonic video game series released by Sega, as well as in numerous spin-off comics, cartoons, and a feature film. The first game was released on June 23, 1991, to provide Sega with a mascot to rival Nintendo's...
) is involved in the separation of the single eye field into two bilateral fields. Although not proven, it is thought that shh emitted from the prechordal plate suppresses Pax6
PAX6
Paired box protein Pax-6 also known as aniridia type II protein or oculorhombin is a protein that in humans is encoded by the PAX6 gene.- Function :PAX6 is a member of the Pax gene family...
which causes the eye field to divide into two. If the shh gene is mutated, the result is cyclopia, a single eye in the center of the face (Gilbert, 2000).
Notable cases
A British description from 1665 of a coltColt (horse)
A colt is a young male horse, under the age of four. The term "colt" is often confused with foal, which refers to a horse of either sex under one year of age....
apparently suffering from cyclopia reads:
First, That it had no sign of any Nose in the usual place, nor had it any, in any other place of the Head, unless the double Bagg CC that grew out of the midst of the forehead, were some rudiment of it. Next, That the two Eyes were united into one Double Eye which was placed just in the middle of the Brow.
On December 28, 2005, a kitten with cyclopia, "Cy", was born in the Redmond
Redmond, Oregon
Redmond is a city in Deschutes County, Oregon, United States. Incorporated on July 6, 1910, the city is located on the eastern side of Oregon's Cascade Range, in the High Desert, and is considered the geographical heart of Central Oregon...
, Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and died about one day after birth.