HDCN Ask the Professor: Genetic counseling for a pregnant woman with ADPKD

Question: I have a 31 year old patient with polycystic disease (ADPKD). She has normal renal function and she is normotensive at 18 weeks into her first pregnancy. Her brother, who is 28 years old, has the same disease, and her father died at 55 after living 4 years with a kidney transplant (ADPKD diagnosis established when he was 45 years old). The patient asked me what the chances were of her child having ADPKD. What is the usefulness of getting the genetic test and what is it's sensitivity, even if she wants to continue her pregnancy?

Richard Turcot MD (Trois Rivieres, Quebec)


Response by Dr. William M. Bennett, Professor of Medicine, Oregon Health Sciences University, Portland, OR:
Assuming that the patient has typical ADPKD and that her husband does not have the disease, the chances of her passing on the abnormal gene to her child are 50%. With normal renal function and blood pressure at 18 weeks, the chances for an uncomplicated pregnancy and delivery are excellent for the mother and fetus. If the patient's family is genetically informative, linkage analysis could with about 85-90% accuracy tell if the fetus carries the ADPKD1 gene. However, this test is expensive, relatively difficult to arrange and, most importantly, should not alter a physician's advice about this situation. Specifically, there is no indication for pregnancy interuption even if the fetus carried the gene, since ADPKD is usually compatible with a symptom free course until midlife or longer. Even with early onset ADPKD, most experts would not terminate a pregnancy in the situation described. (December, 1995)

References

Chapman AB, Johnson AM, Gabow PA. Pregnancy outcome and its relationship to the progression of renal failure in autosomal dominant polycystic disease. JASN 5:1178-1185, 1994.

Gabow PA, Grantham J, Bennett WM, et al. Gene testing in autosomal dominant polycystic disease: results of an NKF workshop. Am J Kidney Dis 13:85-87, 1989.

(December, 1995)

Just to make this case more challenging lets add that there is a strong history of Cerebral aneurysms. I had a similar situation 2 years ago. Would you screen this female patient prior to her pregnancy for aneurysm, and if she had a 2mm positive finding what would you do?
Ari Kostadaras, M.D. (arimd@ix.netcom.com)
Astoria, N.Y. -Thursday, May 30, 1996 at 20:31:23 (CDT)

The chance for aneurysm rupture depends on the size of the aneurysm. A 2 mm aneurysm has a very low rupture potential (the magic cutoff seems to be 10 mm). Furthermore, a 2 mm lesion can be detected only with angiography, since CT or MRI angio give false negative results for aneurysms that are less than 5 mm. From what is described I would not screen such a patient.
William Bennett, MD
Portland, OR USA-Friday, May 31, 1996 at 09:20:04 (CDT)

The important issue to my mind is not the question of advice tothe woman who is already pregnant. Rather, what is the correct advice to a woman with a family history as described. Should she avoid pregnancy?
Dr Clive H Gold
Zefat, - Saturday, August 08, 1998 at 00:52:55 (PDT)