Excerpt from Turner Syndrome
Synonyms, Key Words, and Related Terms: Turner syndrome, Turner's syndrome, 45,X karyotype, Bonnevie-Ullrich syndrome, gonadal dysgenesis, monosomy X, XO syndrome, short stature, Leri-Weill dyschondrosteosis, coarctation of the aorta, aortic dissection, diabetes mellitus, hypertension, osteoporosis, urinary tract infections, aortic valve disease, mitral valve disease, subacute bacterial endocarditis, SBE, Noonan syndrome, gonadoblastoma, amenorrhea, ovarian failure, webbed neck, cubitus valgus, Madelung deformities, shield chest, lymphedema, otitis media, Crohn disease, ulcerative colitis, scoliosis, bicuspid aortic valve, hypothyroidism, cystic hygroma, horseshoe kidney
Please click here to view the full topic text: Turner Syndrome
Background
In 1938, Henry Turner first described Turner syndrome, which is one of the most common chromosomal abnormalities.1 More than 95% of adult women with Turner syndrome exhibit short stature and infertility.
Pathophysiology
Turner syndrome is caused by the absence of one set of genes from the short arm of one X chromosome. In patients with 45,X karyotype, about two thirds are missing the paternal X chromosome. In addition to monosomy X, a similar clinical picture is found with a 46,XXiq karyotype and in some individuals with mosaic karyotypes. A deletion of the SHOX gene can cause a similar skeletal phenotype known as Leri-Weill dyschondrosteosis.
Frequency
United States
The frequency is approximately 1 in 2000 live-born female infants.2 As many as 15% of spontaneous abortions have a 45,X karyotype.
International
The incidence is the same as in the United States. No known ethnic or racial factors influence frequency.
Mortality/Morbidity
- Mortality may be increased in the neonatal period because of coarctation of the aorta and in adulthood because of cardiovascular disease, particularly aortic dissection. Obesity, with associated diabetes mellitus and hypertension, can also contribute to early mortality. Limited epidemiologic studies suggest that life expectancy is reduced by about 10 years. Osteoporosis is common.
- Renal anomalies found in some individuals may cause a predisposition to urinary tract infections or hypertension. Even in the absence of cardiac or renal anomalies, patients are prone to develop hypertension.
- Individuals with mitral valve disease or aortic valve disease require subacute bacterial endocarditis (SBE) prophylaxis.
Race
- No racial or ethnic predilections are known.
Sex
- Turner syndrome only occurs in females.
- Noonan syndrome, sometimes inappropriately called male Turner syndrome, can occur in males or females. It is an autosomal dominant genetic disorder and is not a chromosomal disorder. It is unrelated to Turner syndrome.
Age
- As a chromosomal disorder, Turner syndrome is present at conception or following the first cell division and remains throughout life.
- Gonadotropin levels, particularly follicle-stimulating hormone (FSH) levels, may be elevated at birth, although not reliably enough for use in excluding the diagnosis. They are gradually suppressed by about age 4 years, only to rise to menopausal levels after age 10 years.
Please click here to view the full topic text: Turner Syndrome
|
 |
|
