Trisomy 21 : Down Syndrome
Down Syndrome is caused by the presence of an extra copy of chromosome 21 in the cells of a developing baby. Having an extra copy of this chromosome means that individuals have three copies of each of its genes instead of two, making it difficult for cells to properly control how much protein is made. Usually it is not inherited and so a baby can be affected even if there is no family history of Down Syndrome. Any woman can have a baby with Down Syndrome. However, older women are more likely to have a baby with the condition.
Down Syndrome causes delays in physical and mental development of a child. It is associated with mild to moderate intellectual disabilities and may also lead to digestive and heart defects.
Trisomy 18 : Edwards Syndrome
Edwards Syndrome occurs when a person has a third copy of chromosome 18 instead of two. The extra materials from the third copy of the chromosome 18 interfere with the normal two, and affects the development of the fetus. It is a rare chromosome abnormality that affects approximately one in every 5,000 to 10,000 live births. These children have severe developmental delay, as well as severe birth defects and health problems involving nearly every organ system in the body. Edwards Syndrome occurs more frequently in female than male.
There are various symptoms of Edwards Syndrome. Some of these symptoms include clenched hands, crossed legs, having feet with rounded bottom, the baby being born with a low birth weight, and low set ears. The risk of having a baby with Trisomy 18 increases slightly with the mother’s age. However, the average age of the mother at delivery of a baby with Trisomy 18 is 32 years. In general, in each subsequent pregnancy the chance of having another baby with Trisomy 18 is no greater than 1%. It is difficult to predict the life expectancy of a baby with Edwards Syndrome.
Trisomy 13 : Patau Syndrome
Patau Syndrome is caused by having an extra copy of the chromosome 13. The extra chromosome 13 causes severe neurological and heart defects which make it difficult for infants to survive. Patau Syndrome carries a high risk of misscarriage and approximately 80% of children born with this defect die shortly after birth. The exact incidence of Patau syndrome is not known, although it appears to affect females more than males, most likely because male fetuses do not survive until birth. It causes many physical and mental abnormalities such as heart defects, unusual facial features, small head, missing eyes, low set ears, extra fingers and toes and spinal defects. Patau Syndrome occurs in about 1 in 12,000 births. The risk of having a baby with Trisomy 13 also increased with the mother's age.
Treatment of Patau Syndrome focuses on the particular physical problems with which each child is born. Many infants have difficulty surviving the first few days or weeks due to severe neurological problems or complex heart defects. Surgery may be necessary to repair heart defects or cleft lip and cleft palate. Physical, occupational, and speech therapy will help individuals with Patau Syndrome reach their full developmental potential.
Microdeletion syndromes are defined as a group of clinically recognisable disorders characterised by a small deletion of a chromosomal segment. The size and position of the deletion determine which clinical features are manifested and how severe they are.
5p / Cri-du-Chat:
Also known as 5P deletion sydnrome, babies typically exhibit small head size, low birth weight, decreased muscle tone. and have moderate to severe intellectual disability. Feeding and/or breathing difficulties are also common.
Babies born with 1p36 deletion syndrome typically have weak muscle tone, heart and other organ defects. Most will display developmental problems and varying degrees of intellectual disability.
Babies born with 2q33.1 will typically experience delayed growth and exhibit behavioural developmental problems. Severe feeding difficulties are common and the incidence of cleft palate is also high.
10p13-14 (DiGeorge Syndrome 2):
Babies born with DiGeorge syndrome 2 may present many clinical problems, including cardiac defects, hypoparathyroidism, T-cell immunodeficiency, and facial dysmorphism.
Babies born with 16p12.2-p11.2 deletion syndrome commonly have dysmorphic facial features, feeding difficulties, recurrent ear infections, developmental delay, and cognitive impairment. Additional features, such as heart defects and short stature sometime also occur.
Jacobsen syndrome is a clinically characteristic disorder due to deletion of the terminal band 11q23. Common features of the syndrome are growth delay, psychomotor problems, a broad nasal bridge, short nose with anteverted nostrils, carp-shaped upper lip, low-set dysmorphic ears and other limb dysmorphia.
Van der Woude Syndrome:
Van der Woude syndrome is caused by a mutation in a single gene with equal distribution between the sexes. The clinical symptoms vary but may include lower lip pits with cleft lip and cleft palate.
Prader-Willi / Angelman Syndrome:
Angelman syndrome is a neurodevelopmental disorder characterized by mental disability, movement or balance disorders, and severe limitations in speech and language. Most cases are caused by absence of a maternal contribution to the imprinted region on chromosome 15q11-q13. Prader-Willi syndrome is a clinically distinct disorder resulting from paternal deletion of the same 15q11-q13 region and results in similar clinical features
SEX CHROMOSOMAL ANEUPLOIDY
Each cell in your body contains 46 chromosomes arranged in 23 pairs. One of these chromosome pairs is known as the sex chromosomes because this pair of chromosomes determines our sex. Sex chromosome abnormalities occur when there are extra, missing, or altered sex chromosomes present.
XXY / Klinefelter Syndrome:
Klinefelter’s syndrome is a genetic condition that only affects males. Affected males have an extra X chromosome.Males with Klinefelter’s syndrome have small testes which do not produce enough of the male hormone testosterone before birth and during puberty. This lack of testosterone means that during puberty, the normal male sexual characteristics do not develop fully. There is reduced facial and pubic hair, and some breast tissue often develops. The lack of testosterone is also responsible for other symptoms, including infertility.
X / Turner Syndrome:
Turner syndrome is caused by a completely or partially missing X sex chromosome in females. Females with Turner syndrome often have a wide range of symptoms and some distinctive characteristics. Two that occur in almost all cases of Turner syndrome are:
-being shorter than average
-underdeveloped ovaries (female reproductive organs), resulting in a lack of monthly periods and infertility.
XXX / Triple X:
Triple X syndrome, also called trisomy X is characterized by the presence of an additional X chromosome in each of a female’s cells. The symptoms and physical features associated with trisomy X vary greatly from one person to another. Some females may have no symptoms (asymptomatic) or very mild symptoms and may go undiagnosed. Other women may have a wide variety of different abnormalities.
Triple X syndrome is associated with an increased risk of learning disabilities and delayed development of speech and language skills. Delayed development of motor skills (such as sitting and walking), weak muscle tone (hypotonia), and behavioral and emotional difficulties are also possible, but these characteristics vary widely among affected girls and women. Seizures or kidney abnormalities occur in about 10 percent of affected females.
XYY / Jacob Syndrome:
XYY, sometime called Jacob syndrome, affects only males and is caused by the presence of an extra Y chromosome. Affected individuals are usually very tall. Many experience severe acne during adolescence. Additional symptoms may include learning disabilities and behavioural problems such as impulsivity.