Gonadal dysgenesis (XO)
Turner syndrome is a genetic condition thatonly affects females. It is caused by an abnormal sex chromosome and affects about 1 in every 2,000 baby girls.
Babies are usually born with 23 pairs of chromosomes. One pair of chromosomes determines the baby's sex. This pair are known as the sex chromosomes.
One sex chromosome comes from the father and the other one comes from the mother. The mother’s contribution is always an X chromosome. The father’s contribution can either be an X or a Y chromosome.
A baby girl usually has two X chromosomes (XX) and boys have an X and a Y chromosome (XY). The Y chromosome determines ‘maleness’, so if it is missing as in Turner syndrome, the sex of the child will invariably be female.
A female with Turner syndrome has part or all of one X chromosome missing. This means the girl has just one complete X chromosome rather than two.
Characteristics of Turner syndrome
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
As height and sexual development are the two main characteristics, Turner syndrome is often undiagnosed until a girl reachespuberty (sexual maturity).
Other characteristics of Turner syndrome can vary significantly between individuals. For example, the syndrome can sometimes cause heart, kidney and thyroid problems, as well as bone disorders and ear problems.
Treating Turner syndrome
There is no cure for Turner syndrome, but many of the associated symptoms can be treated.
Girls and women with Turner syndrome will need to have regular health checks throughout their lives. However, it is usually possible to lead a relatively normal and healthy life.
Life expectancy is slightly reduced but it can be improved if regular health checks are maintained and any potential problems are identified and treated at an early stage.
Turner syndrome is caused by a completely or partially missing X sex chromosome in females
Types of Turner syndrome
Turner syndrome is named after Dr Henry Turner who first described it in 1938.
Depending on how much of a female's X chromosome is missing, the syndrome can either be described as:
classic Turner syndrome – where one of the X chromosomes is completely missing
mosaic Turner syndrome – where one X chromosome is complete in most cells, but the other is partially missing or abnormal in some way; in some cells, there may be just one X chromosome or, rarely, two complete X chromosomes
Teen girls 15-18
The symptoms of Turner syndrome vary depending on the age of the girl or woman affected.
Babies born with Turner syndrome often have swollen hands and feet, which is caused by a build-up of excess fluid in the surrounding tissues (lymphoedema). It usually clears up soon after birth.
Other symptoms that may develop before birth include:
thick neck tissue
swelling of the neck (cystic hygroma)
being a small baby
Common characteristics of Turner syndrome
The most common characteristics of Turner syndrome are:
ovaries that do not work properly
These affect over 9 out of 10 females with the condition and are described below in more detail.
Babies with Turner syndrome usually grow at a normal rate until three years of age. After this age, their growth rate will be lower-than-average.
At puberty (usually between 8-14 years), a girl with Turner syndrome will not have the normal growth spurt.
On average, adult women with untreated Turner syndrome are 20cm (8in) shorter than adult women without the syndrome. Treatment with growth hormones can reduce this difference.
Ovaries are the pair of reproductive organs in females that produce eggs and sex hormones. During puberty, a girl's ovaries usually begin to produce the sex hormones oestrogen and progesterone.
However, most girls with Turner syndrome will not produce these sex hormones which means that:
unlike other girls, they may not start their monthly periodsnaturally
they may not fully develop breasts
they may be infertile (unable to have a baby)
Even though many women with Turner syndrome have undeveloped ovaries and are infertile, their vagina and womb develop normally. This will mean they are able to have a normal sex life.
Most girls need hormone replacement therapy (HRT) from around 12 years of age in order to begin puberty, including breast development and the start of monthly periods.
About three out of every 10 girls with Turner syndrome experience some physical changes naturally during puberty, and a very small number may be able to become pregnant.
There are many other symptoms or characteristics that can affect girls and women with Turner syndrome. Some of these include:
a particularly short, wide neck (webbed neck)
a broad chest and widely spaced nipples
arms that turn out slightly at the elbows
a low hairline
mouth abnormalities, which can cause problems with the teeth
a large number of moles
small, spoon-shaped nails
a short fourth finger or toe
eyes that slant downwards
droopy eyelids (ptosis)
a squint (strabismus)
lazy eye (amblyopia)
cataracts – cloudy patches in the lens (the transparent structure at the front of the eye)
reoccurring middle ear infections (otitis media) and glue ear during early childhood
hearing loss – which can occur in later life, is often more severe and develops earlier than the normal age-related decline in hearing
Turner syndrome is often associated with a number of other health conditions. Some of these include:
Heart murmur – where your heart makes a whooshing or swishing noise between beats. This is sometimes linked to a narrowing of the main blood vessel in the heart (the aorta).
An underactive thyroid gland (hypothyroidism) – which occurs in around 10-30% of women with Turner syndrome. Regular blood tests are needed to detect it early.
High blood pressure (hypertension) – blood pressure also needs to be checked regularly.
Osteoporosis (brittle bones) – which may develop due to the lack of oestrogen. HRT can often help prevent osteoporosis.
Scoliosis (abnormal curvature of the spine) – occurs in about 1 in 10 teenage girls with Turner syndrome and should be screened for.
Diabetes – a lifelong condition that causes a person's blood sugar level to become too high.
Lymphoedema – as well as affecting unborn babies, lymphoedema can occur at any age.
Gastrointestinal bleeding (bleeding in the digestive system) – due to abnormalities in the blood vessels in the intestines.
Other digestive conditions – such as Crohn's disease andulcerative colitis are also more common in females with Turner syndrome.
Kidney and urinary tract problems – which can increase the risk of developing urinary tract infections (UTIs).
Most girls with Turner syndrome have good language and reading skills. However, some have behavioural, social and specific learning difficulties that are often overlooked by doctors. These are discussed below.
About a third of girls with Turner syndrome have problems understanding social relationships due to the way their brain develops.
This can make it difficult to sustain friendships and lead to relationship problems in later life, both at home and at work.
Girls and women with Turner syndrome tend to be anxious and eager to please. This can make them vulnerable because they may be naive or lack experience in dealing with particular situations. As adults, many women with Turner syndrome prefer to work with children.
Spatial awareness and numeracy
Spatial awareness is the ability to understand where you are in relation to objects or other people. More than 8 out of 10 females with Turner syndrome have difficulty understanding spatial relationships. This may cause problems when learning to drive or when following directions on a map.
A similar number have some degree of difficulty learning or understanding maths. This is known as dyscalculia. School teachers may not fully appreciate the problem, which can cause considerable stress.
Attention and hyperactivity problems
Typically, girls with Turner syndrome will go through a phase in childhood that involves:
physical overactivity, such as constant fidgeting and restlessness
acting impulsively, such as breaking rules or having no sense of danger
having a short attention span and being easily distracted
Attention and hyperactivity problems usually begin when the girl is a toddler. However, they may not be a serious problem until the girl starts school at four or five years of age. Girls with Turner syndrome may have difficulty settling in class.
Medicines that are usually given to treat symptoms of attention deficit hyperactivity disorder (ADHD) may not be as effective in cases of Turner syndrome.
The physical hyperactivity usually reduces around the age of 11, although problems with innattention can last longer, into the teens.
Causes of Turner syndrome
Turner syndrome is a genetic condition caused by abnormal sex chromosomes.
One of the female sex chromosomes (see below) is either missing or incomplete. This causes abnormalities as the baby develops in the womb, as well as developmental problems following birth, such as short height, ovarian that do not work properly and learning disabilities.
Chromosomes are made up of strands of DNA. Each cell in the human body contains 23 pairs of chromosomes.
Chromosomes carry genes (genetic material) that are inherited from your parents and determine your physical appearance and behavioural characteristics. Medical conditions can also be inherited through faulty chromosomes.
The sex chromosomes determine whether a baby will be male or female. They can either be X or Y chromosomes. You inherit one chromosome from each parent, with a female usually having two X chromosomes (XX), and a male having one X and one Y chromosome (XY).
Missing or incomplete X chromosome
Turner syndrome occurs when a baby is conceived. It only affects females who have a missing or incomplete X chromosome. If a baby is conceived with a missing X chromosome, the pregnancy will not usually develop and an early miscarriage occurs.
Approximately 95% of pregnancies conceived with Turner syndrome will end in miscarriage. However, there are many reasons for miscarriages. Overall, Turner syndrome is thought to be responsible for around 15% of miscarriages.
Who is at risk?
Turner syndrome is a fairly rare condition, affecting about 1 in every 2,000 baby girls.
Females of all races, nationalities and regions of the world can get Turner syndrome. It appears to occur randomly and is not linked to the mother’s age. It is also very rare to have a second child with Turner syndrome.
There are no known poisonous chemicals or environmental factors that cause Turner syndrome or increase the likelihood of a baby having it.
Diagnosing Turner syndrome
Turner syndrome is usually identified during childhood or at puberty. However, it can sometimes be diagnosed before a baby is born.
Pregnancy and birth
Turner syndrome may be suspected in pregnancy during a routine ultrasound scan (where high frequency sound waves are used to create an image of the developing baby).
Lymphoedema, a condition that causes swelling in the body’s tissues, can affect unborn babies with Turner syndrome, and may be visible on an ultrasound scan.
If Turner syndrome is suspected, further prenatal tests can confirm it, such as:
chorionic villus sampling – a sample of cells is taken from the placenta and tested for genetic conditions; the placenta is the organ that links the mother’s blood supply to her unborn baby’s
amniocentesis – a sample of amniotic fluid is tested for genetic conditions; amniotic fluid is the fluid that surrounds the developing baby in the womb
Sometimes Turner syndrome is diagnosed at birth as a result of heart or kidney problems, or swelling of the hands and feet (lymphoedema).
If a girl has the typical characteristics and symptoms of Turner syndrome, such as a webbed neck, broad chest and widely spaced nipples, the syndrome may be suspected.
Short height and undeveloped ovaries are the two main features of Turner syndrome, so it's often identified during early childhood when these features become noticeable.
In some cases, Turner syndrome is not diagnosed until puberty (sexual maturity) when breasts don't develop and monthly periods do not start.
A child’s height is usually closely related to the height of their parents. Girls with Turner syndrome are typically short in relation to the height of their parents. So, an affected girl who has two tall parents may be taller than some of her peers, and is less likely to be identified based on her poor growth.
Karyotyping is a test that involves analysing chromosomes (the thread-like structures inside all human cells).
Karyotyping is often used where Turner syndrome is suspected. The test can either be carried out while the baby is inside the womb by taking a sample of amniotic fluid, or it can be carried following birth by taking a blood sample.
Treating Turner syndrome
There is no cure for Turner syndrome, but many of the associated symptoms can be treated.
Regular health checks and preventative care and treatment are important for girls and women with Turner syndrome. This is because of the risk of complications.
Some hospitals have dedicated Turner syndrome clinics with a number of specialists including:
an ear, nose and throat (ENT) specialist – who will monitor the ears with regular hearing assessments
a paediatric endocrinologist – a specialist in conditions that affect hormones and metabolism (the process that turns food into energy) in children and teenagers
an adult endocrinologist – a specialist in conditions that affect hormones and metabolism in adults
a cardiologist – a heart specialist
an obstetrician – a specialist in pregnancy and birth
a gynaecologist – a specialist in treating conditions that affect the female reproductive system
If a girl or women is diagnosed with Turner syndrome, the following areas may be monitored throughout her life.
Hearing and ears
During childhood, middle ear infections (otitis media) are more likely to develop and need to be treated quickly. About half of all women with Turner syndrome lose their hearing at a faster rate compared with normal age-related decline.
High blood pressure (hypertension) is quite common in women with Turner syndrome, so it's important that blood pressure is regularly checked and treated, if necessary.
Thyroid function tests can be used to assess how well your thyroid gland is working, as there is also a slightly higher risk of having anunderactive thyroid (hypothyroidism).
The glucose levels in your blood or urine may be checked to screen fordiabetes (a lifelong condition that causes your blood sugar level to become too high).
Bone mineral density (BMD)
Women with Turner syndrome have an increased risk of developingosteoporosis (brittle bones). Your bone mineral density can be measured using a dual energy X-ray scan, which is usually known as aDEXA scan.
If you are diagnosed with any of the above conditions, you will be given appropriate treatment.
Growth hormone therapy
An endocrinologist (specialist in hormone-related conditions) will be able to carry out tests and checks on a regular basis. They will also be able to recommend appropriate treatment, such as growth hormone therapy.
Growth hormone therapy should be given to a girl with Turner syndrome as soon as it becomes apparent that she is not growing normally. It will help prevent short height during adulthood.
Growth hormone therapy is usually started around five or six years of age. However, it may be started later. Growth hormone therapy will usually continue until the girl is 15 or 16 years of age.
The National Institute for Health and Care Excellence (NICE) has produced guidance about somatropin, the growth hormone sometimes used to treat Turner syndrome.
There are a number of different types of somatropin available. The type used will be based on the needs of the individual following a discussion with the specialist, including any advantages and disadvantages of the treatment.
Treatment with somatropin should be stopped if:
there is not enough growth in the first year of treatment
the girl is near to her final height and has grown less than 2cm (0.8in) in a year
the girl is unable to continue taking the medicine due to side effects
the girl reaches her final height
Somatropin is usually given daily as a single injection. Parents can the injection or the girl can be taught to do it herself. The dose will depend on the girl’s size.
The studies reviewed by NICE found that somatropin increased height by around 5-9cm (2-3.5in).
Oestrogen and progesterone replacement therapy
An endocrinologist may also recommend oestrogen and progesterone replacement therapy.
Oestrogen and progesterone are the female hormones responsible for sexual development. Oestrogen is also important in preventingosteoporosis (brittle bones).
In girls with Turner syndrome, the sex hormones do not work properly and the ovaries (the female reproductive organs) do not produce enough oestrogen.
Women with Turner syndrome will usually need regular sex hormone treatment until about 50 years of age. After this time, the body usually stops producing oestrogen and monthly periods stop. This is known as the menopause.
Oestrogen replacement therapy is usually started at the time of normalpuberty or just after. In girls, this is around 11 years old. It may be recommended oestrogen is started between the ages of 12 and 15, because starting treatment too early may reduce the final height the girl is able to grow to.
Oestrogen can trigger the changes that usually happen during puberty, such as breast development, which, otherwise, girls with Turner syndrome may not experience.
Oestrogen can be given as a tablet, patch or injection. Low doses are used to start with before being gradually increased until the girl’s oestrogen levels become normal.
Progesterone replacement therapy is usually started slightly later than oestrogen and can help encourage a girl's monthly periods to start.
Most women with Turner syndrome are infertile (unable to have children). A minority will be able to coneive naturally, so girls and women with Turner syndrome should have access to sexual health and contraception advice.
Assisted conception techniques, such as in vitro fertilisation (IVF), may be recommended for women with Turner syndrome who want to have children.
If a woman has Turner syndrome and becomes pregnant, she will need regular heart checks because the heart and blood vessels will be put under extra strain during pregnancy.
Some girls and women with Turner syndrome may develop psychological problems, such as low self-esteem or depression.
Doctors sometimes attribute these problems to physical appearance or infertility, but they are more commonly related to difficulties understanding other people’s social behaviour and how to respond appropriately. Associated problems commonly arise at home, in school and in the workplace.
Psychological therapy, such as counselling or cognitive behavioural therapy (CBT), may be recommended.
Most girls with Turner syndrome have a normal level of intelligence, but some may have learning difficulties and require extra tuition at school or home.
It's important to seek help if your daughter is affected. Not all aspects of ability are affected equally so an experienced psychologist should be asked to give an opinion.
You can speak to your GP or health visitor, or the teacher at your child’s school or nursery. The school or nursery should follow guidelines about how to assess and meet your child’s special educational needs to ensure she gets the appropriate support.
Help and support
The Turner Syndrome Support Society is a UK-based charity that provides information, care and support for girls and women with Turner syndrome.