Trisomy X (Triple X Syndrome)

Affects one in 1,000 females

Triple X syndrome results from an extra copy of the X chromosome in each of a female’s cells. Females with this condition may be taller than average, but it typically causes no unusual physical features. Most females have normal sexual development and are able to conceive children. There is an associated risk of learning disabilities and delayed development of speech, language and motor skills. Seizures or kidney abnormalities occur in about 10% of affected females.

Monosomy X (Turner Syndrome)

Affects one in 2,500 females

Most often, Turner syndrome results when one X chromosome is normal and the other X chromosome is missing or altered.The most common feature of Turner syndrome is short stature, which becomes evident by about age 5. An early loss of ovarian function is also very common. Up to half of affected females are born with a heart defect, complications of which can be life threatening. However, most girls and women with the condition have normal intelligence.

XXY (Klinefelter Syndrome)

Affects one in 500 to 1,000 males

Most often, Klinefelter syndrome is the result of at least one extra copy of the X chromosome in each cell. The condition interferes with sexual development, such as reduced levels of testosterone, which can lead to delayed, or incomplete puberty, breast enlargement, reduced facial and body hair, and infertility. It also causes abnormal functioning of the testes.

XYY (Jacobs Syndrome)

Affects one in 1,000 males

Jacob’s syndrome is the result of one extra copy of the Y chromosome in each cell. Although males with this condition may be taller than average, this chromosomal change typically causes no unusual physical features. Most have normal sexual development and are able to father children.There is an increased risk of learning disabilities and delayed development of speech, language and motor skills. A small percentage of males are diagnosed with autistic spectrum disorders, which are developmental conditions that affect communication and social interaction.

5p deletion syndrome
(Cri du Chat Syndrome)

Affects one in 20,000 to 50,000 newborns

This condition results when a piece of chromosome 5 is missing. Affected infants have a high-pitched cry that sounds like a cat, hence the name Cri-du-chat (cat’s cry).It causes intellectual disability and delayed development, small head size, low birth weight, and weak muscle tone in infancy. Affected individuals also have distinctive facial features, including widely set eyes, low-set ears, a small jaw and a rounded face. Some infants with Cri-du-chat syndrome are born with a heart defect. As they grow, people with cri-du-chat usually have difficulty walking and talking. They may have behavioural problems and severe intellectual disability.

1p36 deletion syndrome

Affects one in 5,000 to 10,000 newborns

This condition results when a piece of chromosome 1 is missing, and typically causes severe intellectual disability. Most affected individuals have limited or no speech, as well as behaviour problems. Most have structural abnormalities of the brain resulting in seizures. There may also be weak muscle tone and swallowing difficulties. Physical characteristics include a small head that is also unusually short and wide in proportion to its size. There might also be vision or hearing problems, and abnormalities of the skeleton, heart, gastrointestinal system and other organs.

2q33.1 microdeletion syndrome

This rare condition results when a piece of chromosome 2 is missing. It affects the motor neurons, which are the specialised nerve cells in the brain and spinal cord that control the movement of muscles. The disorder usually causes severe mental retardation and behaviour problems.

16p12.2 deletion syndrome

This condition results when a piece of chromosome 16 is missing. Common clinical features for 16p12.2 deletion includes: a delay in starting to speak, a degree of developmental delay or learning difficulty, growth impairment, a cardiac malformation, epilepsy and mild dysmorphic facial features without a consistent pattern.

11q23 microdeletion syndrome
(Jacobsen Syndrome)

Affects one in 100,000 newborns

Jacobsen syndrome, which is also known as 11q terminal deletion disorder, is caused by a deletion of genetic material at the long (q) arm of chromosome 11. Most affected individual have delayed development in motor skills and speech, with most having cognitive and learning difficulties and distinctive facial features such as small/low set ears, widely set eyes and large head size. More than 90% of people with Jacobsen syndrome have bleeding disorder call Paris-Trousseau syndrome that causes lifelong risk of abnormal bleeding and easy bruising.

1q32.2 microdeletion syndrome
(Van der Woude Syndrome)

Affects one in 35,000 to 100,000 newborns

Van de Woude syndrome is a condition that affects the development of the face. Many people with this disorder are born with a cleft lip, a cleft palate (an opening in the roof of the mouth), and have an increased risk of delayed language development, learning disabilities, or other mild cognitive problems. Van der Woude syndrome is usually caused by mutations in the interferon regulatory factor 6 (IRF6) gene which is typically encoded in region on chromosomes

15q11.2 microdeletion syndrome
(Prader Willi / Angelman Syndrome)

Angelman syndrome affects one in 12,000 newborns whereas Prader Willi syndrome affects one in 20,000 to 50,000 newborns

Most mothers carrying babies with a 15q11.2 microdeletion experienced no pregnancy problems, had a normal delivery and only discovered their baby was affected after the birth. There are two main types of syndrome associated with this microdeletion. Angelman syndrome results from a loss of gene activity (expression). Main characteristics of Angelman syndrome includes severe mental retardation, lack of speech, excessive happy demeanour.
Prader Willi syndrome is caused by a loss of active genes in a region of chromosome 15. People can have either Prader-Willi syndrome or Angelman syndrome. Characteristics of Prader-Willi syndrome includes mild to moderate development delay, delayed to no puberty.