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Questions and Answers
What is the prevalence of Turner syndrome in the genetically female population in the US?
What is the prevalence of Turner syndrome in the genetically female population in the US?
- Approx. 1:10,000
- Approx. 1:500
- Approx. 1:2,500 (correct)
- Approx. 1:5,000
What is the most common cause of ovarian dysgenesis and primary ovarian insufficiency?
What is the most common cause of ovarian dysgenesis and primary ovarian insufficiency?
- Klinefelter syndrome
- Polycystic ovary syndrome
- Premature ovarian failure
- Turner syndrome (correct)
What is the karyotype of Turner syndrome resulting from meiotic nondisjunction?
What is the karyotype of Turner syndrome resulting from meiotic nondisjunction?
- 46,XX
- 45,XO (correct)
- 47,XXX
- 45,XYY
What is the effect of sex chromosomal mosaicism on the phenotype of Turner syndrome?
What is the effect of sex chromosomal mosaicism on the phenotype of Turner syndrome?
What is the possibility of pregnancy in individuals with Turner syndrome?
What is the possibility of pregnancy in individuals with Turner syndrome?
What is the most common cardiovascular abnormality associated with Turner syndrome?
What is the most common cardiovascular abnormality associated with Turner syndrome?
What is the karyotype most commonly associated with gonadoblastoma in Turner syndrome?
What is the karyotype most commonly associated with gonadoblastoma in Turner syndrome?
What is the primary cause of short stature in Turner syndrome?
What is the primary cause of short stature in Turner syndrome?
Why is it necessary to evaluate for X-linked recessive conditions in patients with Turner syndrome?
Why is it necessary to evaluate for X-linked recessive conditions in patients with Turner syndrome?
What is the primary reason for removing streak gonads in Turner syndrome?
What is the primary reason for removing streak gonads in Turner syndrome?
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Study Notes
Epidemiology
- Prevalence of Turner syndrome: approximately 1 in 2,500 genetically female individuals in the US
Etiology
- Caused by chromosomal nondisjunction during meiosis or mitosis
- Meiotic nondisjunction: complete sex chromosomal monosomy (45,XO; no Barr body)
- Mitotic nondisjunction of an embryonic cell: sex chromosomal mosaicism (45,XO/46,XX) with mild phenotypic expression
Pathophysiology
- Chromosomal nondisjunction → X chromosome monosomy/mosaicism
- Impaired ovarian development → malfunctioning streak gonads with connective tissue instead of normal germ cells
- Estrogen and progesterone deficiencies
Clinical Features
- Female phenotype
- Primary ovarian insufficiency with:
- Delayed puberty
- Primary amenorrhea
- Infertility (pregnancy possible via IVF with donor oocytes and exogenous estradiol 17β and progesterone)
- Lymphatic system abnormalities:
- Cystic hygroma
- Lymphedema of the hands and feet in neonatal period
- Musculoskeletal findings:
- Short stature (due to presence of only one copy of the SHOX gene)
- Shield chest
- Webbed neck
- Cubitus valgus
- Short fourth metacarpals/metatarsals
- Nail dysplasia
- High arched palate
- Low-set posterior hairline
- Cardiovascular abnormalities:
- Bicuspid aortic valve
- Coarctation of the aorta with brachial-femoral delay
- Aortic dissection and rupture
- Hypertension
Associated Disorders
- Gonadoblastoma (especially in patients with 45,XO/46,XY mosaicism)
- Malformations of the kidney and ureters (especially horseshoe kidney)
- Hashimoto thyroiditis
- Type 2 diabetes mellitus
Diagnostics
- Clinical presentation: hypergonadotropic hypogonadism (↓ estrogen, ↓ androgens, ↑ FSH, ↑ LH)
- Karyotyping: confirmatory test
Treatment
- Estrogen and progestogen substitution
- Growth hormone (GH) therapy
- Surgical removal of streak gonads
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