Turner Syndrome
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Turner Syndrome. Synonyms and related keywords. 45 X Karyotype syndrome. Bonnevie-Ullrich syndrome. Gonadal dysgenesis. Monosomy X. History.  Henry Turner, 1938  Ford et al ., 1959. Frequency. 1 in 2,000 live-born female infants.

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Turner Syndrome

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Turner Syndrome


Synonyms and related keywords

  • 45 X Karyotype syndrome.

  • Bonnevie-Ullrich syndrome.

  • Gonadal dysgenesis.

  • Monosomy X.


History

Henry Turner, 1938

Ford et al., 1959


Frequency

  • 1 in 2,000 live-born female infants.

  • 15% of spontaneous abortions have a 45,X0 Karyotype.

    In Sudan ?

    Race

    No racial or ethnic predilections.


Genetic mechanisms

1. Absence of one copy of X chromosome.

 Paternal loss in 62%

 Maternal in 48%

2. Patient with Mosaic karyotype.

 Ex. 46,XX/45,X

3. Structural rearrangement result in loss of

Xp material.

Ex. 46,iX(Xq)

4. Loss of the SHOX gene.

 Variety of Turner syndrome.


45, X0 – Turner syndromes

99% of cases

– aborted

Total fetal

hydrops

1 in 2,500 or

1 in 2,000

liveborn females.

normal intelligence;

may have 3D spatial problems

or math problems.

http://www.gfmer.ch/Genetic_diseases/Turner_syndrome/Turner.htm


Web of skin

Aorta

Breast development

Under- developed ovaries


Phenotype

95% of adult with

Turner syndrome

exhibit short stature

and infertility.


Short stature


Infertility

94% of patients are infertile

Pregnancy has been achieved by:

1. Fresh embryo.

2. Frozen embryo transfer.

Delivery by caesarean section is

related to small pelvic outlet size.


Patients may present with

Ovarian failureprimary amenorrohoae.Undeveloped breast.

45,X[6]/46XX [80]


Patients may present with

Ambiguous genitalia


Ambigious genitalia

  • Age

  • 7 month

  • Sex

  • Male

  • Diagnosis

  • Intersex

  • Examination

  • Big phallus,

  • Labia major.

  • Small L. minora.

  • Blind vagina.

  • Male urethra.

  • Ultrasound

  • NO uterus.

  • Testes could be identified.

46,X,del(X)(p11)[11].


Low hairline.Shield-shaped chest.Narrow hip development.

Patients may present with

.


Lymphedema

  • May be present at any age.

  • It is the cause of the webbed neck and low

    posterior hairline.

  • In infants, the combination of dysplastic or

    hypoplastic nails and lymphedema gives a

    characteristic sausage-like appearance to the fingers and toes.


Patients may present with

Lymphedema

The toes have the characteristic

sausage-like appearance


Generalized lymphedema. Loose skin folds around the neck will form a webbed neck later in life


Hyperconvex nails in Turner syndrome note U-shaped cross section


Mortality and morbidity

Mortality

Is high due to:

1. Coarctation of the aorta.

2. Cardiovascular disease.

3. Obesity, associated diabetes and hypertension.

4. Osteoporosis.

Life expectancy is reduced by 10 years.

Morbidity

Individuals with mitral or aortic valve disease require

prophylaxis for sub acute bacterial endocarditis (SBE).


Nephrology or urology

  • 35% of patients have renal anomalies.

  • Ultrasound evaluation at the diagnosis.

  • Yearly urine culture.

  • BUN, and creatinine.

  • Girls with horseshoe kidneys:

  • Have an increased risk of Wilms tumor.

  • Should have renal ultrasound examinations:

  • Every 5 months until the age of 8 years.

  • Every 6-12 months thereafter.


Audiology

Hearing assessment

At birth

At 1 year-age.

Before entering school.

 At adulthood.


Cardiology

A cardiologist should evaluate patients at diagnosis.

1. Risks of aortic root dilatation.

2. Risks of Aortic dissection.

Complete cardiovascular evaluation

For all patients prior to attempting

assisted reproduction or conception.


Endocrinology

Supplement with:

1. Growth hormone.

2. Estrogens.

3. progestins.

Attention should be paid to:

1. Growth and development,

2. Thyroid status

3. Osteoporosis.

Patients on growth hormone should be seen every 3-4 months.


Other

  • Gastrointestinal bleeding:

  • Hip dislocation:

  • Scoliosis in 10% of adolescent girls with Turner syndrome.

  • Thyroid: 10-30% develop hypothyroidism.


Diagnosis

Should be considered in Individuals with :

  • Primary or secondary amenorrhea.

  • Adult women with unexplained infertility

  • Unexplained short stature.

    Turner syndrome may be diagnosed prenatally by:

    1. Amniocentesis.

    2. Chorionic villous sampling.


Diagnosis

  • The clinical suspicion

  • Cytogenetic analysis

    • 45,X.

    • 45, X/46, XX.

    • 46,XX,del(X)(P10).

  • FISH analysis.

  • Cytogenetic analysis of fibroblas

  • in case of normal karyotype 46,XX.


FISH


45, X0 – Turner syndromes

  • Short Stature (approximately 4 feet 8 inches) –;

    loss of action SHOX gene on the X-chromosome.

  • No ovarian function or early loss of function (in late teens)

  • Coarctation of the aorta (narrow aorta) 10-15%

  • Kidney problem (Horseshoe kidney)  high blood pressure

treated by growth hormone

estrogen-progesterone treatment

to maintain secondary sexual development

Corrected surgically


Medical Care

In childhood

Growth hormone

therapy is standard

to prevent short stature

as an adult.

Cecilia takes her daily growth hormone injection


"My name is Regina and I’m 9 years old. I felt that taking my growth hormone injection was a bit difficult in the beginning, but I practiced with an orange and after a while I found out how to do it, and now it’s just a habit like brushing your teeth."


Estrogen replacement

  • Therapy is required, but starting too

    early can compromise adult height.

  • Estrogen usually is started from

    age 12-15 years.


Surgical Care

Keloid formation

Prophylaxis is required prior to and

dental or surgical procedure in women

with cardiac valve disease, to prevent

subacute bacterial endocarditis.

Turner syndrome individuals exhibits

high risk of keloid formation.

Subacute bacterial endocarditis


Surgical Care

Before

After surgery


Diet

  • Ovarian failure are risk factors for osteoporosis thus adequate daily intake of calcium (1.0-1.5 g) and vitamin D (at least 400 IU) should consider.

  • Patients with short stature require fewer calories than those of normal height.


Genetics counseling

  • Turner syndrome is not an inherited

    disorder, and the recurrence risk is low.

  • Due to infertility, it is rarely passed to

    offspring.

  • Consultation with a geneticist

    1. Suspected mosaicism for all, or part

    2. Virilization with part of Y chromosome.


Prognosis

  • Overall prognosis is good.

  • Even with growth hormone therapy, most

    individuals will be shorter than average.

  • Turner syndrome is not a cause of mental

    retardation.

    Life expectancy is slightly shorter.

    Almost all individuals will be infertile, but

    pregnancy with donor embryos is possible.


Medical and legal pitfalls

  • Yearly follow-up TSH tests will help avoid unrecognized hypothyroidism, which can interfere with growth.

  • Osteoporosis and aortic arch dissection are known complications in adulthood.


Dosage Compensation

  • Shouldn’t XX females produce twice the amount of X-linked gene products (proteins) as XY males?

  • No, because XX females “compensate” by inactivating one of their X chromosomes to make a single “dosage” of X-linked genes.


Barr Bodies are inactivated X chromosomes in Females

Normal female,

Klinefelter male

Normal male,

Turner female

0

1

2

3

# Barr bodies=

N-1 rule


Inconsistencies between syndromes

and X inactivation

  • If normal XX female has one X inactivated,

  • why is a X Turner female not normal?

  • Similarly, if XXY male has one X

  • inactivated, why does he have Klinefelter

  • syndrome?

Perhaps not complete inactivation or

inactivation does not happen immediately,

Then some overexpression of X-linked genes


The Lyon Hypothesis of X Inactivation

  • Proposed by Mary Lyon and Liane Russell (1961)

  • Which X is inactivated? Inactivation of X chromosome occurs randomly in somatic cells during embryogenesis

  • Progeny of cells all have same inactivated X chromosome as original, creating mosaic individual


Lyon-Hypothesis: X-inactivation

A precursor cell to all coat color cells

Random inactivation early in dev.

**Also in calico cats


Inactive Xs condense to form Barr bodies during development

Inactivation is random during development

Color pattern seen in female calico cats due to random X chromosome inactivation

Barr bodies in female cells

X chromosome inactivation

  • X chromosome has many more genes than the Y chromosome

  • Females have 2 Xs

  • One X must be inactivated to preserve gene dosage


Mosaicism Reveals the Random Inactivation of one X chromosome

Anhidroticectodermal

dysplasia in a heterozygous woman

Regions where

sweat glands

are absent.


Thank you


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