Triploidy and Hydatidiform moles

Question 1

Triploidy is the :

Answer 1

term used for an additional set of chromosomes resulting in a count of 69 (3n).

Question 2

Incidence of triploidy in recognised pregnancies

Answer 2

1-3%

Question 3

How many spontaneously abort during the first trimester of pregnancy or are lost during the second trimester as a fetal death in utero

Answer 3

99.9%

Question 4

Liveborn triploid life expectancy

Answer 4

<1 month. V rare

Question 5

2 paternal and one maternal set of chromosomes is called:

Answer 5

Type 1 triplody-Diandry. cystic villi with trophoblastic hyperplasia =partial hydatidiform mole (paternal extra)

Question 6

Most common triplody is:

Answer 6

(60-80%) partial hydatidiform mole

Question 7

Diandric triploids can arise from:

Answer 7

• Majority =fert of a normal egg by 2 sperm (dispermy)

* Minority= fert of a normal egg by a diploid sperm

Question 8

Partial moles survive in utero to:

Answer 8

~12 weeks, placenta develops classical partial hydatidiform mole structure at around 6 weeks.

Question 9

2 maternal and one paternal set of chromosomes is called:

Answer 9

DIgyny Tyoe 2 triplod

Question 10

Digynic triploids can arise from:

Answer 10

• Fertilisation of a diploid egg by a haploid sperm
• Retention of a polar body
• Fertilisation of ovulated primary oocyte
• Fusion of 2 eggs and fertilisation by a haploid sperm

Question 11

Whats is the differing clinical presentation of diandric/digynyic triploidy is presumed to reflect?

Answer 11

the influence of differing imprinted states

Question 12

Digynic (maternal) Vs Diandric (paternal) features

Answer 12

Digynic (maternal) Diandric (paternal)
More likely to survive to second trimester >90% of partial hydatidiform moles
IUGR (often asymmetric) Symmetrical IUGR with structural abs including neural tube defects
Large Head Normal head size
Small placenta (without cystic formation) Large placenta (cystic)
Oligohydramnios Oligohydramnios
Holoprosencephaly -
- High maternal hCG
- Increased risk of pre eclampsia

Question 13

Recurrence risks

Answer 13

• Mostly sporadic
• Recurrence risk is not increased above that of the general population
• Diandric triploidy with partial mole; 1-1.5% risk
• Digynic triploidy – recurrent in a few families

Question 14

Hydatidiform moles can either be partial or complete-what is the difference?

Answer 14

Partial moles are triploid, can either be Diandry or Digyny.
Complete moles are diploid and result form two sperm fertilizing an empty egg. Form of gestational trophoblastic disease with the possibility of malignant transformation.

Question 15

Two ways in which complete moles can arise?

Answer 15

o 20% - dispermic fertilisation (two sperm fert empty egg; can be either XX or XY)
o 80% - monospermic fertilisation (single sperm fert with the male pronucleus dividing to form a diploid nucleus; can only be XX as YY zygotes lack essential genes on X chromosome necessary for development).

Question 16

How do molar pregnancies present ?

Answer 16

painless vaginal bleeding in the fourth to fifth month. uterus may be larger than expected, or the ovaries may be enlarged. There may also be more vomiting than would be expected. • Blood tests will show very high levels of hCG

Question 17

Hydatidiform mole recurrence risk

Answer 17

1:100 Recurrence can be either of the same (complete or partial) or of the other type

Question 18

Recurrence risk following two consecutive complete Hydatidiform moles

Answer 18

1:5 Recurrence can be either of the same (complete or partial) or of the other type

Question 19

Which two genes are known to be associated with Familial recurrent hydatidiform moles (FRHM)

Answer 19

NLRP7 at 19q13.42 and KHDC3L at 6q13. Both have roles in maintaining the maternal imprint within the ovum

Question 20

How does a familial recurrent hydatidiform mole differ from a sporadic complete hydatidiform mole?

Answer 20

diploid and are genetically biparental in origin with both a maternal and paternal contribution. Come about through mutations in NLRP7 and KHDC3L

Question 21

Familial recurrent hydatidiform moles (FRHM) recurrence?

Answer 21

75% of their pregnancies develop as a complete hydatidiform moles. very unlikely to achieve any normal healthy pregnancies.

Question 22

Why does neoplastic transformation of moles occur?

Answer 22

recessive allele is unmasked by a double paternal complement or abnormal imprinting may also have a role in the malignant potential

Question 23

How many patinets with CHM require treatment with chemotherapy?

Answer 23

10%

Question 24

What is the risk of invasion following complete and partial moles?

Answer 24

15%-20% complete, 0.5% partial (low)

Question 25

Invasive Mole presentation?

Answer 25

high HCG following molar pregnancy, swelling and bleeding.

Question 26

what is a gestational Choriocarcinoma?

Answer 26

Highly invasive malignant tumour of the uterine wall

Question 27

What is the risk of choriocarcinoma following complete and partial moles?

Answer 27

~3%complete mole, 0.1% partial

Question 28

What is the treatment and monitoring for GTD?

Answer 28

Suction evacuation is for complete and partial moles. hCG levels monitored via weekly blood test. 2 years complete , 6 months following partial. hCG should drop to normal range within 8 weeks. Chemotherapy recommended if:
o Metastases in brain, liver, GI, lung found on XR
o Histological evidence of choriocarcinoma
o Rising or raised levels of hCG