Genetics - a whole new world

1 in 4. Those are our chances of having a baby with NKH.

Nonketotic hyperglycinemia, or NKH, is a very rare genetic disorder, caused by a defect in a child’s genetic coding which means that they can’t break down Glycine. Glycine is an amino acid that is found naturally in our bodies and we need it to grow and develop properly, but when it’s not broken down and accumulates, it effectively becomes poisonous. The result is severe disruption to movement and development, brain damage, seizures and muscle weakness. Children with NKH tend not reach milestones past those reached by a regular 6-week-old infant. It’s not pretty. It’s terminal and most born with the disorder will die in early infancy.

In Leo’s case, as in 95% of cases, he inherited one gene mutation from Rich and one from me, causing the perfect storm in his little body. And as both Rich and I are carriers for NKH, there is a 1 in 4 chance, with each pregnancy, of it happening again. Not cool.


Since Leo died, we’ve been on a self-taught crash course in genetics and it’s truly fascinating. Luckily, the brilliant doctors in Miami took blood samples from Leo before he passed so that we could dig a little deeper into the specific genetic mutations that he inherited from us, and because genetics is still an emerging field, Rich and I qualified for free follow up family testing.

We have since had an extraordinary number of blood tests and been able to establish exactly what is that Rich and I each carry in order to make educated decisions about our future family planning options. We’ve been fortunate to work with some brilliant laboratories and doctors along the way - including the head researcher for NKH who kindly mapped Rich’s mutation to provide some important details to the genetics counsellors we’ve been working with. Ladies and gentlemen, this is a gene! The red dot is the mutation…obviously.

But joking aside, there are 24,000 genes in the human body and over 6,000 known single gene disorders. While NKH itself is rare, 1 in 200 babies is born with a genetic disorder.

As I said, I’ve enjoyed the learning process during our quest for answers following Leo’s death and we’ve found a lot of comfort in the “science” surrounding his disorder but it’s also highlighted how utterly clueless we were about how humans are put together. Given the number of questions I get asked on almost a daily basis but friends and colleagues, it would appear that we’re not the only ones - so here’s a 60 second recap of high school biology for you:

Genes are segments of DNA that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are structures within cells that contain a person's genes.

  • Every human cell contains 23 pairs of chromosomes, for a total of 46 chromosomes.

  • Each chromosome contains hundreds to thousands of genes.

  • A trait is any gene-determined characteristic and is often determined by more than one gene.

  • Some traits are caused by abnormal genes that are inherited or that are the result of a new mutation.

Leo inherited two mutations from us in the GLDC gene and although the mutations and that Rich and I carry are different, the fact that they’re both in the same gene causes the issue.

Leo lewis NKH genetics

We’re now going through a process of having a special gene probe built for our specific mutations, but I’ve also had a general carrier screening test done which is a blood test that screens for 274 of the more “common” genetic disorders to see whether I’m a carrier for anything else…

In the US these tests are covered almost entirely by insurance, but if you ask me they should be given out for free to anyone who is thinking about getting pregnant. Knowledge is power I say and the more we can know about our genetic makeup I think the better - if only to prepare ourselves. It wouldn’t have occurred to me to take a detailed look into my genetic background before we had Leo, and even if we had we wouldn’t have uncovered NKH, but I still think it’s important that people consider the fact that certain disorders aren’t uncommon and a simple look at your family tree might reveal something that’s better considered before you make the life changing decision to have children. Often genetic disorders can be treated and it’s just a case of arming yourself with the facts in advance.

What’s also fascinating about genetics is that it’s a field that’s growing incredibly quickly - just 2 or 3 years ago geneticists would have had very few resources to help a family like us, yet here we are with clear answers as to exactly what caused Leo’s disorder, as well as solid options for the future. Geneticists all over the world share data to inform each others’ work and we have donated all of our results and Leo’s medical records to help advance their research. I really do hope that as more data gets added to their pool, they can find even more answers to help other people as well as cures for some of the monstrous disorders like NKH. They’re now able to screen for cancer causing mutations in families with a history of certain illnesses - their research and knowledge is saving lives and it’s awesome. With the immense potential of genetics in dealing with currently incurable diseases, serious research is being done into correcting gene abnormalities or replacing defective genes with correct ones through gene therapy - it’s so bloody clever and exciting.

Geneticists are some of the most remarkable people I’ve ever come across. The work they’re doing is groundbreaking and I can’t wait to see what they discover over the next few years. We’re told that the information we have about Leo, and specifically Rich’s gene mutation, has added a new insight into what geneticists know about NKH - I guess that’s just part of his little legacy :)

Leos legacy

You can read more about NKH, the research being done and find support here.