Ask Dr. Dan is a blog series that features Dr. Dan Doherty, who since 2004 has been researching Joubert syndrome through the University of Washington Hindbrain Malformation Research Program.
But since this edition focuses on kidney-related questions, Dr. Dan recruited someone well-qualified to help tackle them: Dr. John Sayer, nephrologist and long-time Joubert kidney disease researcher at Newcastle University in the United Kingdom.
The questions below come from the parents of a 9-year-old boy with TMEM67-related Joubert syndrome, who was recently diagnosed with kidney involvement. To submit your questions for a future blog post, email them to info@jsrdf.org (be sure to note that your question is for Ask Dr. Dan).
For JS kids, what is the rate of kidney failure, compared to the general population? Is it faster? Our son is at Stage 3 CKD (chronic kidney disease) now. What are the chances of him staying there vs. getting to Stage 5 and needing a transplant?
We don’t have precise data to answer this question. The kidney disease most often associated with TMEM67-related Joubert syndrome is called nephronophthisis. Nephronophthisis is the most common genetic cause of kidney failure within the first three decades of life, so yes it does progress and cause more problems than other types of childhood kidney issues. Typically, in nephronophthisis, kidney scarring occurs and causes reduced kidney function which worsens over time and patients ultimately progress to stage 5 kidney disease (kidney failure). It’s impossible to predict when children will reach stage 5 kidney disease but the average is around 15 years of age, although there is a wide spread from less than 5 years to over 30 years. Your doctor can use blood results to create a plot or graph of kidney function and this can be used to predict progression in a specific patient. Early in the course of kidney trouble, we provide supportive treatments to keep children healthy. Some patients benefit from dietary changes and others need oral medicines for high blood pressure. When the kidneys can no longer keep up with the body’s needs, patients and their families have to decide what kind of treatments make sense in the context of the child’s overall condition. Some families opt for dialysis, a treatment where machines are used to replace the kidney’s usual functions, and often this is used as a bridge to a kidney transplant. Kidney transplantation requires a donated kidney from an immunologically matched living or deceased donor. A comprehensive medical and surgical work up is involved which can take many months.
For JS kids, how successful are kidney transplants, compared to the general population?
Again, we don’t have a lot of data to answer this question, but in our experience, most kids with JS do as well (or better) than other patients following transplantation. In addition, nephronophthisis, the kidney disease most often seen in JS, does not come back in the transplanted kidney. Our experience is supported by small studies from Japan, although the follow-up time was limited.
What kind of survival rate are we looking at here?
With good medical care, children with nephronophthisis survive a long time, but they are at risk for having complications associated with dialysis and kidney transplant. Kidney dialysis requires lots of medical support and may be complicated by infections and technical problems. Kidney transplantation is complicated by the risk of organ rejection which can occur at any time point, and by the required immunosuppressant medications, which can lead to increased risk of infections and other serious side effects. Some of these complications can result in shortened lifespan. That said, a well-matched kidney in an otherwise healthy recipient is expected to last 15-20 years. Some patients may require 2 or 3 kidney transplants over a lifetime, and some also need dialysis treatment in the time between consecutive kidney transplants.
