Prenatal diagnosis (PND) in Joubert syndrome

1. Prenatal diagnosis (PND) in Joubert syndrome

2. Goals of PND • Provide reassurance/reduce uncertainty • Prepare for the birth of an affected child • Delivery route • Delivery location • Emotional preparation • Assure the birth of an unaffected child • Pregnancy termination • (Preimplantation genetic diagnosis) • Allow for prenatal treatment

3. JS is autosomal recessive* Recurrence risk = 25%

4. Reproductive options • Accept the risk without PND

5. Reproductive options • Accept the risk without PND • Accept the risk and consider PND: • To prepare for an affected child • To terminate an affected pregnancy

6. Reproductive options • Accept the risk without PND • Accept the risk and consider PND: • To prepare for an affected child • To terminate an affected pregnancy • Sperm or egg donor to reduce risk

7. Reproductive options • Accept the risk without PND • Accept the risk and consider PND: • To prepare for an affected child • To terminate an affected pregnancy • Sperm or egg donor to reduce risk • Choose to adopt

8. Reproductive options • Accept the risk without PND • Accept the risk and consider PND: • To prepare for an affected child • To terminate an affected pregnancy • Sperm or egg donor to reduce risk • Choose to adopt • Choose not to have additional children

9. Reproductive options • Accept the risk without PND • Accept the risk and consider PND: • To prepare for an affected child • To terminate an affected pregnancy • Sperm or egg donor to reduce risk • Choose to adopt • Choose not to have additional children ALL of these choices are valid.

10. Risk scenarios • Prior affected child: 25% risk each pregnancy • Clinical diagnosis only -> prenatal imaging • Clinical and genetic diagnosis -> genetic testing and prenatal imaging • No family history: population risk (very low) • Routine prenatal care • Population risk of birth defects 2-3%

11. Testing Strategies • Available • Prenatal imaging • Fetal DNA testing (amniotic fluid or CVS) • Not Available • Maternal serum screening • Biochemical testing (amniotic fluid)

12. Imaging diagnosis • Consistent finding • Cerebellar vermis hypoplasia • Molar tooth sign not seen before 24 weeks • Supportive findings (rare) • Polydactyly • Cystic kidneys • Encephalocele • Increased respiratory rate

13. Vermis hypoplasia US Superior vermis intact Inferior vermis absent

14. Vermis hypoplasia fetal MRI 21 wks Affected 22 wks Unaffected

15. Molar tooth sign in utero 29 wks gestation Post-natal

16. Polydactyly in utero 2 3 1 4 5 6 Aslan et al. 2002

17. Encephalocele in utero US (not JS) Fetal MRI (JS)

18. Specific imaging strategy • Usual prenatal care and screening • Consultation with a tertiary care center • 16-18 week US • 20 week US • 20-22 week fetal MRI adapted from Doherty et al. 2005 We are happy to consult with OB providers/radiologists about imaging diagnosis. We prefer to be involved starting before/early in the pregnancy.

19. Imaging diagnosis • Advantages: • Non-invasive • Can visualize brain, fingers, kidneys • Can be repeated throughout pregnancy • Relatively inexpensive • Disadvantages: • Technician-dependent • Radiologist-dependent • May not see subtle abnormalities • Late diagnosis

20. Background: Genetic Testing Gene Estimated frequency NPHP1 ~2% AHI1 ~10% CEP290 ~10% RPGRIP1L ~5% MKS3 ~10% ARL13B <1% CC2D2A ~10% INPP5E ? TMEM216 ~ 4% MKS1 ~ 2% OFD1 <1% TOTAL <50% Frequency of mutations in patients with JS

21. DNA testing strategy • Test affected child prior to next pregnancy

22. DNA testing strategy • Test affected child prior to next pregnancy • Test affected child prior to next pregnancy

23. DNA testing strategy • Test affected child prior to next pregnancy • Test affected child prior to next pregnancy • No mutation identified -> PND by imaging

24. DNA testing strategy • Test affected child prior to pregnancy • Test affected child prior to pregnancy • No mutation identified -> PND by imaging • Mutation identified • Preimplantation genetic diagnosis • Chorionic villous sampling • Amniocentesis

25. DNA collection techniques • early placental tissue • 10-12wk gestation • Risks: • Miscarriage (1/100) • Infection • Less available in US • DNA dx 12-14 wks Chorionic villus sampling

26. DNA collection techniques Amniocentesis • fetal skin cells in fluid • >15 wk gestation • Risks: • Miscarriage (1/500) • Infection • Fluid leak • Fetal injury • DNA dx ~20+ wks

27. Making a Decision • Genetic Counselor or Geneticist can help • Discuss options • Provide resources and support • Consider contacting them before pregnancy or early in pregnancy • See www.nsgc.org for a list of local GC’s

28. Conclusions • Family history of JS • Known mutation -> PND by gene testing • No mutation -> PND by prenatal US & fetal MRI • No family history • JS not distinguishable from other cerebellar vermis hypoplasias before 24wks • Variable features can facilitate diagnosis • Encephalocele, polydactyly, cystic kidneys • After 27wks, dx possible by imaging alone

29. Acknowledgements University of Washington Joubert Center http://depts.washington.edu/joubert/ 206-616-3788 joubert@uw.edu