Turner syndrome
Turner syndrome, also known as 45XO or 45X, is the most common of the sex chromosome abnormalities in females.
Epidemiology
The incidence is estimated at 1:2000-5000 of live births, although the in utero rate is much higher (1-2% of conceptions) due to a significant proportion of fetuses with 45X aborting by the 2trimester.
Clinical presentation
In adults, it is one of the most important causes of primary amenorrhea and accounts for approximately one-third of such cases.
Pathology
Genetics
Turner syndrome is classically characterized by the absence of one X chromosome copy (45 XO), with the missing chromosome most frequently (two-thirds) being the paternal one. Most cases occur as a sporadic event.
However, the classic genetic change is not present in all cases. Three main subtypes include:
- complete monosomy (45XO): ~60%
- even though it is relatively common, almost all 45 XO fetuses will spontaneously abort, with 70% lost between 16 weeks and term
- partial monosomy (structurally-altered X chromosome): ~15%
- mosaicism (XO and another sex karyotype): ~30%
Unlike the common trisomies, there is no association with maternal age.
Markers
- serum alpha-fetoprotein (AFP): decreased
- beta HCG
- elevated if hydrops present
- decreased if no hydrops
- serum inhibin
- elevated if hydrops present
- absent if hydrops absent
Associations
- hypertension
- glucose intolerance
- inflammatory bowel disease
- hypothyroidism: due to the formation of thyroid antibodies (most commonly Hashimoto thyroiditis)
- gonadal dysgenesis / ovarian dysgenesis
Complications
In utero complications include:
- development of hydrops fetalis: usually from fluid overload secondary to lymphatic failure
Radiographic features
Antenatal ultrasound
- cystic hygroma: may appear septated; one of the most typical features of Turner syndrome
- increased nuchal thickness
- increased nuchal translucency
- coarctation of the aorta: 15-20%
- bicuspid aortic valve
- horseshoe kidney / pelvic kidney
- mild IUGR
- features related to complicating hydrops fetalis
- short fetal limbs
Postpartum-to-adulthood features
Musculoskeletal
- scoliosis
- short 4metacarpal: positive metacarpal sign
- narrowing scapholunate angle: positive carpal sign
- abnormal medial femoral condyle
- decreased carpal angle: Madelung deformity
- short stature
- webbed neck
- valgus deformity of the elbow: increased carrying angle (cubitus valgus)
Pelvic ultrasound
- streaky uterus
- streak ovary
Gastrointestinal
Treatment and prognosis
Overall prognosis very variable is dependent on associated anomalies. While the vast majority of fetuses are aborted in the second trimester, some may have a long life expectancy. Cases with mosaicism do much better. Mental development is unaffected.
History and etymology
It is named after the American endocrinologist Henry H Turner (1892-1970) who first described the syndrome in 1938.
Differential diagnosis
General differential considerations include:
- Noonan syndrome: can have similar phenotypical features but normal karyotype
Siehe auch:
- Aortenisthmusstenose
- Skoliose
- Hufeisenniere
- Hydrops fetalis
- Chronisch-entzündliche Darmerkrankungen
- nuchal translucency
- Bikuspidalität der Aortenklappe
- Arterielle Hypertonie
- Intrauterine Wachstumsretardierung
- trisomies
- nuchal thickness
- Noonan-Syndrom
- Hashimoto-Thyreoiditis
- gonadal dysgenesis
- zystisches Lymphangiom
- Madelung-Deformität
- metacarpal sign
- positive carpal sign
- hydrops
und weiter:
- Karpale Koalition
- Hypertelorismus
- obstetric curriculum
- Ebstein anomaly
- Herzfehler
- Varianten der Herzanatomie
- Os carpale
- Mikrognathie
- Klinodaktylie
- einseitige Nierenagenesie
- chromosomale Anomalien
- fetal pleural effusion
- absent nasal bone
- Brachymetatarsie
- orbital hypertelorism
- altered alpha fetoprotein levels
- Gesichtsdysmorphie
- verzögerte Skelettreifung
- calcifying epithelioma of Malherbe
- absent ductus venosus
- differential diagnosis of osteoporosis
- Störungen der geschlechtsspezifischen Entwicklung
- Antekubitales Pterygiumsyndrom
- short metacarpals (mnemonic)
- Verkürzung Metakarpale vier oder fünf
- madelung deformity associations (mnemonic)
- disorder of sex development
- Dyschondrosteose Léri Weill