Trisomy 9 is a chromosomal disorder

Genetic disorder

A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....

 caused by having three copies (trisomy

Trisomy

A trisomy is a type of polysomy in which there are three copies, instead of the normal two, of a particular chromosome. A trisomy is a type of aneuploidy .-Description and causes:...

) of chromosome number 9. It can appear with or without mosaicism.

Characteristics

Symptoms vary, but usually result in dysmorphisms in the skull

Human skull

The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...

, nervous system

Nervous system

The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...

, and mental retardation

Mental retardation

Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...

. Dysmorphisms in the heart

Heart

The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

, kidneys, and musculoskeletal system may also occur. An infant with complete trisomy 9 surviving 20 days after birth showed clinical features including a small face, wide fontanelle

Fontanelle

A fontanelle is an anatomical feature on an infant's skull.-Anatomy:Fontanelles are soft spots on a baby's head which, during birth, enable the bony plates of the skull to flex, allowing the child's head to pass through the birth canal. The ossification of the bones of the skull causes the...

, prominent occiput

Occiput

The occiput is the anatomical term for the posterior portion of the head, in insects the posterior part of those head capsule.-Clinical significance:Trauma to the occiput can cause a basilar skull fracture....

, micrognathia, low set ears, upslanting palpebral fissures, high arched palate

Palate

The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...

, short sternum, overlapping fingers, limited hip abduction, rocker bottom feet, heart murmurs and also a webbed neck.

Trisomy 9p is one of the most frequent autosomal anomalies compatible with long survival rate. A study of 5 cases showed an association with Coffin%E2%80%93Siris syndrome, as well as a wide gap between the 1st and 2nd toes in all five, while three had brain malformations including dilated ventricles

Ventricular system

The ventricular system is a set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal of the spinal cord.-Components:The system comprises four ventricles:* right and left lateral ventricles* third ventricle...

 with hypogenesis of the corpus callosum

Corpus callosum

The corpus callosum , also known as the colossal commissure, is a wide, flat bundle of neural fibers beneath the cortex in the eutherian brain at the longitudinal fissure. It connects the left and right cerebral hemispheres and facilitates interhemispheric communication...

 and Dandy-Walker malformation.

Detection

Trisomy 9 can be detected prenatally

Prenatal diagnosis

Prenatal diagnosis or prenatal screening is testing for diseases or conditions in a fetus or embryo before it is born. The aim is to detect birth defects such as neural tube defects, Down syndrome, chromosome abnormalities, genetic diseases and other conditions, such as spina bifida, cleft palate,...

 with chorionic villus sampling

Chorionic villus sampling

Chorionic villus sampling , sometimes misspelled "chorionic villous sampling", is a form of prenatal diagnosis to determine chromosomal or genetic disorders in the fetus. It entails sampling of the chorionic villus and testing it...

 and cordocentesis, and can be suggested by obstetric ultrasonography

Obstetric ultrasonography

Obstetric sonography is the application of medical ultrasonography to obstetrics, in which sonography is used to visualize the embryo or foetus in its mother's uterus...

.

Because trisomy 9 may appear with mosaicism, it is suggested that doctors take samples from multiple tissues when karyotyping for diagnosis.

External links

• NORD - National Organization for Rare Disorders, Inc. Chromosome 9, Trisomy 9p (Multiple Variants)
• NORD - National Organization for Rare Disorders, Inc. Chromosome 9, Trisomy Mosaic
• MaggiBlair.com Maggi Blair - Trisomy 9 Mosaic Syndrome

TRISOMY 9p / Mosaic Trisomy 9 / Trisomy 9 duplication / chromosome 9 / Survey on Trisomy 9*[http://www.trisomy9.org]