Turner syndrome

Question 1

What happens to 95% of Turner conceptuses?

Answer 1

They fail to reach term

Question 2

What are the three keys feature of turners syndrome detected in Utero?

Answer 2

1. Cystic hygroma: excess fluid at nape of neck
2. Massive lymphadema: due to failure of lymphatic drainage
3. Intrauterine growth restriction

Question 3

What are the clinical features of Turners syndrome in a newborn?

Answer 3

• Small
• lymphadema of hands and feet (residue of in Utero condition)
• nail hypoplasia (results from lymphadema)
• excess skin at nape of neck

Question 4

What are the 4 major clinical features of Turners syndrome in childhood?

Answer 4

• Short stature (98%)
• high arched palate (82%)
• short neck/low hairline (80%)
• hypoplastic widely spaced nipples (78%)

Question 5

What are the common features of classical Turner syndrome (45,X)?

Answer 5

• Congenital heart malformations
• Structural anomalies of the kidneys
• short stature
• Streak ovaries
• primary amenorrhoea
• Infertile
• Delayed puberty with no secondary sexual development

Question 6

What are the common cytogenetic causes of Turner syndrome?

Answer 6

• 55% = 45,X
• 25% = 46,X,abnormal X (12-20% = 46,X,i(X)(q10))
• 15% (at least) = mosaic (either numerical or structural)

Question 7

How is the Turner phenotype affected when a numerical mosaic is involved?

Answer 7

• May have milder phenotype
• May be taller
• May enter puberty spontaneously
• Likely to have secondary amenorrhoea/premature menopause rather than primary amenorrhoea
• may be fertile/sub fertile

Question 8

How is the Turner phenotype affected when a structural mosaic is involved?

Answer 8

• may show fewer of the turner stigmata and may only show short stature and gonadal dysgenesis

Question 9

What are the three main structural mosaics observed in Turner syndrome?

Answer 9

• Isochromosome Xq: 46,X,i(X)(q10)
• Ring chromosome: 46,X,r(X)
• deletion of Xq: 46,X,del(Xq)

Question 10

How can the presence of marker chromosomes affect Turner mosaic individuals?

Answer 10

• If Y derived then there may be elevated risk of Gonadoblastoma
• If X derived then generally have classic Turner features but if X-inactivation centre is absent on marker they may have more severe phenotype due to failure of X inactivation resulting in functional disomy. Severity of phenotype depends on genes present

Question 11

What is the treatment strategy for Turner syndrome?

Answer 11

• Growth hormone treatment
• Oestrogen and progesterone to develop secondary sexual characteristics
• fertility issues combatted by oocyte donation, gamete or embryo transplant
• if y material present then surgery to remove streak ovaries due to elevated Gonadoblastoma risk

Question 12

What is the incidence of Turner syndrome?

Answer 12

1:2000 to 1:5000 liveborn girls

Question 13

What are the recurrence risk to parents in Turners syndrome?

Answer 13

• If 45,X then recurrence risk is low - parental samples not requested.
• However, if there is a structurally abnormal second X then maternal sample is required for karyotyping to estimate recurrence risk

Question 14

What are the recurrence risk to offspring in Turner syndrome?

Answer 14

• Natural fertility rare but more common if mosaic
• increased risk of trisomy 21 and 45,X
• If structural rearrangement involved there is a high recurrence risk and possibility of male foetal loss

Question 15

What is the difference between proximal and distal Xq deletions in Turner syndrome?

Answer 15

• Proximal deletions usually more severe with primary amenorrhoea and failure to enter puberty.
• With distal deletions menarche may occur but premature ovarian failure may develop (early menopause)