My daughter, son-in-law, and I suspect my 5-year-old grandson have Noonan’s Syndrome. It was ruled out by a blood test when he was 2, but he has so many markers and nothing else has been found that matches his collection of issues. He has been held back a year from starting school because of his developmental delay. Have you any advice as to who we could go to for further exploration? Is he too young for a cardiac ultrasound to be useful in picking anything up? If so, what age would be appropriate?
The best thing is to get a referral from your GP to the nearest Genetic Clinic. With the concerns about developmental delay, it would be appropriate to do some more general tests, e.g. a detailed chromosome test (chromosome microarray). Most children with Noonan Syndrome have a heart murmur which leads to a detailed scan. The scan can be done at any age, but without a murmur is probably going to be normal. The genetic testing for Noonan Syndrome has changed as more genes have been found, and it is possible the original test only looked at one of the genes, so may be worth repeating.