Cord Blood for Dwarfism Genetic Testing

 

When my husband and I were planning to get pregnant, there was the question of double dominancy for heterozygous dwarfism. My husband has pseudoachondroplasia and I have achondroplasia. We were told why take the risk and even TRY for children if there is a chance of health issues or being incompatible with life. And we felt, why not try? Don’t get me wrong. Talking to our geneticist and OB/GYN definitely got us rattled. But, I was determined to find the answers. In my own research, I found a handful of people with both the pseudo and achon genes who are living a productive, healthy life. Most of them had only a couple of health problems, which was fewer than our son who only has one dwarfism gene. I interviewed these LP adults who were either carriers of both genes or whose child was a carrier of both genes. All of them said that they had the same common surgeries of pseudos or achons. By the time we got pregnant, I distinctly remember a young genetic counselor having a serious talk with us about our pregnancy. She had this solemn look on her face as she went over the punnett square. We smiled and said to her we already knew the probabilities. Coincidentally, our childhood geneticist had walked in to consult with us. When she walked into the room, she smiled and assured the counselor, “They know their stuff.”

We could’ve had amnio done with both children, but we thought the risk was too high to endanger the baby. And what would we do with that information? Ending the pregnancy was out of the question. We felt we would just deal with it once the babies were born. With our son, the ultrasound results showed he was definitely achon (head, trident, etc.), but we weren’t sure if he also had the pseudo gene. We didn’t care and just went forward without further in utero tests. When we got pregnant with our daughter, her ultrasounds didn’t show achon features. But, we knew that pseudos are not diagnosed until 2-3 yo., which was when my husband got diagnosed. When I gave birth to my daughter, we saved the cord blood to do the genetic test. Though we could have looked for the COMP gene, it would be more accurate to match the cord blood against my husband’s blood since he doesn’t show “classic pseudo” features as Dr. Jacqueline Hecht noted. He more resembles MED due to his height and hand features. There was no match for the gene with our daughter. We didn’t care whether or not our children had any dwarfism or the fact that she is Average Height. We just wanted to know without harming the baby with a blood draw. We have a blog entry that talks about genetics.

Some geneticists experienced in dwarfism say that heterozygous dwarfisms (two different dominant genes like achon and pseudo) ARE considered high risk (more health complications, possibility of still birth, etc.) and some say it is not a risk. I know of children with two different dwarfism genes (heterozygous) and one of them is living and healthy. The other had many health complications and passed before the age of 5. But, I never asked that parent what the cause of death was. The LP mom was a friend of mine, who unexpectedly passed within the year.

Is MED and Pseudoachondroplasia considered lethal? From talking to geneticists on LPA’s Medical Advisory Board (MAB) and those who have followed us throughout our lives (experience w/ dwarfism, but not on the MAB), MED and pseudo have similar genetic traits. I don’t know if that would be conisidered homozygous dwarf genes or heterozygous dwarf genes. My husband does not resemble the classic pseudo. That is why we had our children’s blood matched directly with his instead of looking for the COMP gene. If you are even the slightest interested in knowing the baby’s type of dwarfism, you could just save the cord blood and do the genetic test this way. I did this when my daughter was born.

In conclusion, there are several means of determining whether a child has dwarfism. But, the question is: What would you do with that information?

Comments 1

  1. The risks for a child with both achondroplasia and pseudochondroplasia depends on the type of pseudochondroplasia, from what I’ve read. Pseudochondroplasia can be caused by a mutation in the same gene as achondroplasia, or a completely different gene. A child who has achondroplasia and pseudochondroplasia coded by the same gene will have double dominant issues, while a child who has both conditions coded for by two different genes will just have features of both put together and will be about as healthy as someone with only one of those conditions.

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