Turner's syndrome

TURNER SYNDROME

Muni Venkatesh. PGroup 2

Turner syndrome• Turner syndrome (TS): is a genetic condition that

only affects females.

• The condition is caused by an abnormal chromosome and affects about one in every 2,500 baby girls, but is much more common among pregnancies that do not survive to term (miscarriages and stillbirths).

• TS was named after Dr Henry Turner, who discovered the condition in 1938.

How do people get Turner syndrome???

• Turner syndrome is typically caused by nondisjunction.

• a pair of sex chromosomes fails to separate during the formation of an egg (or sperm), so, when an abnormal egg unites with a normal sperm to form an embryo, that embryo may end up missing one of the sex chromosomes (X rather than XX).

• Advanced maternal age is not associated with an increased incidence.

Cont…

Cont…• The abnormality is not inherited from an

affected parent (not passed down from parent to child).

• because women with Turner syndrome are usually sterile and cannot have children.

Types of Turner syndrome• Cases of TS where an X chromosome is

completely missing are sometimes referred to as 'classical' Turner syndrome.

• About 30 percent of girls with the disorder are only missing the X chromosome in some of their cells. This mixed chromosome pattern is known as mosaicism.

• Girls with this pattern may have fewer symptoms because they still have some normal (XX) cells.

Cont…• Y chromosome material: In a small percentage

of cases of Turner syndrome, some cells have one copy of the X chromosome and other cells have one copy of the X chromosome and some Y chromosome material.

• These individuals develop biologically as girls, but the presence of Y chromosome material increases the risk of developing a type of cancer called gonadoblastoma.

Genetics of turner’s syndrome45,X 50%

46,X,i(Xq) 15%

45,X/46,XX mosaics 15%

45,X/46,X,i(Xq) mosaics about 5%

45,X, other X abnormality about 5%

Other 45,X/? mosaics about 5%

Characteristics• Girls and women who have TS often have a wide

range of different medical symptoms, or characteristics.

• However, there are two characteristics that occur in almost all cases of TS. They are:

being shorter than average in height

a lack of development of the ovaries, leading to infertility

Cont…• One of the missing genes on the X chromosome

is the SHOX gene, which is responsible for long bone growth.

• The missing SHOX gene is the reason girls who have the disorder are unusually short.

• Other missing genes regulate ovarian development, which influences sexual characteristics.

• Possible symptoms in young infants include:

Swollen hands and feet

Wide and webbed neck and a low or indistinct hairline

• A combination of the following symptoms may be seen in older females:

Absent or incomplete development at puberty

A broad chest and widely spaced nipples

Drooping eyelids , Dry eyes

Infertility

No periods (absent menstruation)

Short height

Vaginal dryness

Arms that turn out slightly at the elbow

• Short stature (143-145cm tall)• Loss of ovarian function• Hormone imbalances( thyroid, diabetes) • Stress and emotional deprivation• Diseases affecting the kidneys, heart, lungs or

intestines• Bone diseases • Learning problems( esp. in maths)

Clinical features

A heart murmur, sometimes associated with narrowing of the aorta.

A tendency to develop high blood pressure (so this should be checked regularly).

Scoliosis occurs in 10 percent of adolescent girls

The thyroid gland becomes under-active in about 10 percent of women who have Turner syndrome.

Older or over-weight women with Turner syndrome are slightly more at risk of developing diabetes.

Osteoporosis can develop because of a lack of estrogen.

Diagnosis• About half of the cases are diagnosed within

the first few months of a girl's life by the characteristic physical symptoms .(swelling of the hands and feet, or a heart defect).

• Other patients are diagnosed in adolescence because they fail to grow normally or go through puberty.

Cont…• When the doctor suspects Turner syndrome, a

blood sample can be used to make a karyotype and the diagnosis can be confirmed.

Cont…• Turner syndrome may be diagnosed during

pregnancy with a chorionic villus sampling (CVS) or amniocentesis.

• Alternatively, an ultrasound can identify the disorder by its physical symptoms before the baby is born (signs of underdevelopment).

Treatment• Hormone replacement therapy is the best way

to treat this disorder. Teenagers are treated with growth hormone to help

them reach a normal height.

They may also be given low doses of androgens (male hormones which females also produce in small quantities) to increase height and encourage normal hair and muscle growth.

Some patients may take the female hormone estrogen to promote normal sexual development.