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What are the differences between Noonan Syndrome, LEOPARD Syndrome and Costello Syndrome?

User in Boise, ID
May 19, 2017

Hi, I'm in the process of trying to find an accurate diagnosis for my toddler son. We haven't done genetic testing, but I'm wondering of other parents would be willing to share their diagnostic stories - how you got the accurate diagnosis of noonan syndrome and then anything about other related syndromes.

Answers
User in Portland, OR
Aug. 7, 2015

Adelaide, 
The diagnostic journey can be a long and exhausting one, you're doing the right thing by doing research and trying to figure out as much information as you can on your own. I think it's really a process of elimination - some things may be related to a certain syndrome and some things may not be. Have you written down a full list of your child's symptoms and behaviors? That's where I would start, then include any relevant behavior, social, or educational testing information. 

Our son has a congenital heart defect, so that was the first thing that we noticed and that we were focused on. Initially, it was really all that we had to go on. I think it's definitely something that made us overlook other things that were going. For us a congenital heart defect was something that was particularly scary and made us very nervous. 

Noonan Syndrome

As far as Noonan Syndrome goes there are a variety of features and characteristics to consider. It's incredibly interesting because depending on your specific child different things may be present or and the level they affect your child may vary. 

Signs and Symptoms:
  • Congenital heart defect
  • Sunken or protruding chest
  • Short stature - this isn't present at birth or right away, growth tends to slow over time
  • High arched palate
  • Distinctive facial features including widely spaced eyes and low set ears
  • Broad or webbed neck
  • Developmental delays (highly variable)
  • Bleeding disorders and complications
Many specialists have told us that when a child is a toddler and infant, the physical features of Noonan Syndrome are much more noticeable and that they can soften with sage. 

Unfortunately, there's a lot of mystery around the genetics of Noonan Syndrome. It seems like genetic mutations are only identifiable in ~60% of individuals. There are also a variety of mutations, so it's not like there's one specific cause and you have an answer. However, because there are many other conditions that can 'seem like' Noonan Syndrome, genetics can sometimes be a good way of ruling out or ruling in other conditions or syndromes. 

It's very important to get an accurate diagnosis, so you're doing the right thing. If you highly suspect Noonan Syndrome, I suggest seeing a specialist or provider that has experience with Noonan Syndrome (this isn't always easy to find)

LEOPARD Syndrome

Many of the signs and symptoms of LEOPARD syndrome also occur in Noonan Syndrome, so it's important to consider it in your diagnostic journey. Many times it's hard to diagnosis because the signs and symptoms are highly variable. Some of the symptoms I'm going to describe below may or may not be present, making it easy to confuse with Noonan Syndrome.

Signs and Symptoms:
  • Brown skin spots that look like freckles called letigines 
  • Cafe-au-lait spots
  • Short stature and delays in growth
  • Cardiac involvement including congenital heart defects
  • Characteristic facial features including widely spaced eyes, low set ears
  • Developmental delays
  • Genital abnormalities in males
  • Chest Abnormalities
There is some difficulty with diagnosis because Noonan syndrome and LEOPARD syndrome are both caused by mutations in the PTPN11 and RAF1 genes. In addition, LEOPARD syndrome is confused with Neurofibromatosis Type 1 due to the presence of cafe-au-lait spots. 

CFC Syndrome

CFC (craniofaciocutaneous) Syndrome is a condition that affects multiple parts of the body. It can be difficult to diagnose because of the range of symptoms and the fact that there are other similar conditions. While you didn't mention this condition, it's one to look at and consider. 

Signs and Symptoms:
  • Distinctive facial features: widely set eyes, low set ears.
  • Congenital heart defects
  • Skin abnormalities including rough skin and keratosis pilaris
  • Failure to thrive
  • Hypotonia
  • Growth delays
Three different genes have been found to be associated with CFC syndrome (BRAF, MEK1, MEK2), so genetic testing may be able to eliminate this condition as a possibility.

Costello Syndrome

While this condition is considered similar to Noonan Syndrome, the tendency for those affected by tumors is a big differentiator. In Costello Syndrome, there is an increased likelihood of developing both cancerous and non-cancerous tumors. 

Signs and Symptoms:
  • Growth delays and short stature
  • Cancerous and non-cancerous tumors
  • Flexible joints
  • Hypotonia
  • Skin abnormalities including hyper-pigmentation and loose skin
  • Heart problems including congenital heart defects
Genetic testing for mutations in the HRAS gene is available to confirm the diagnosis of Costello syndrome. 

I hope that this helps you with understanding some of the similarities and differences, and hopefully it's beneficial on your diagnostic journey.
User
Sept. 10, 2015

Do you think it's possible that some kids are diagnosed with Noonan's and actually have something else?

User in Toledo, OH
Sept. 16, 2016

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