1. Balanced Translocations
Karuna Sapru
Arshad Siddiqui
Janet Smillie
Alison Teo
The case of Mr and Mrs Snow and
their Christmas Baby Wish

2. Dear Dr Claus,
I would be very grateful if you could see Mr and Mrs Snow in your clinic
who have been trying for a baby for some time now. Unfortunately, Mrs
Snow has suffered three first trimester miscarriages and the couple are
finding it hard to come to terms with this. There is a positive family
history on the paternal side with Mr Snow’s mother suffering from two
miscarriages. His sister is also in very early pregnancy and may also
therefore benefit from cytochromal genetic analysis and a referral to
your clinic.
I have arranged for lupus anticoagulant and anticardiolipin antibody
studies and a cytogenetic chromosomal analysis for each partner and
the results should now be available to you. On further discussing the
situation with the couple I have mentioned the possibility of a genetic
cause for their recurrent miscarriages with this being the reason for
their referral to your clinic for further information.
I hope you are able to help this couple.
Yours sincerely,
Dr. S. Leigh

3. History
• Personal
• Family History
– Affected and at risk relatives
– Automimmune disease
Why does miscarriage happen?
– Uterine abnormalities
– Immunologic reasons
– Medical (thyroid, DM)
– PCOS
– Infection
– Lifestyle
– Genetics
• Commonest – trisomy 16

4. Pedigree
?

5. Genes are found
in paired
chromsomes
Each parent has 23
chromosome pairs and a
pair of sex chromosomes
Each parent passes on one
chromosome from each
pair to their offspring

6. Normal DeletionBalanced Deletion
Mrs Snow Mr Snow

7. Balanced
• Same as Mr Snow
• Risk Multiple Myeloma

8. Deletion of
chromosome 4p
Wolf-Hirschhorn Syndrome
Mental retardation
Cleft lip/palate - feeding difficulties
Microcephaly and seizures
Poor muscle tone
Characteristic facies
-hypertelorism
-down turned mouth
-small chin
WHSC1 geneWHSC1 gene

9. Deletion of
chromosome 14q
•Few described cases
•Overlapping toes
•Pointed chin
•Congenital heart anomaly
•Excess neck skin
•High vaulted palate
•Narrow palate
•Small jaw
•Developmental delay
•Seizures

10. Options
• Genetic Ix
• Preimplantation genetic Dx
• CVS
• amniocentesis

11. Different Situations
• Spontaneous
mutation or
inherited?
• If unbalanced
translocation
• Sister
– Test for translocation

12. Merry Christmas