Last year my son had a rare neurological condition that he is now recovering from and I will tell you now I have taken possibly a decade off my life due to the obsessive Googling I did, I also believe it is partly responsible for me having to take anti-depressants for 8 months. Dr Google is vicious and he will not help, you will only concentrate on the worst possibilities ignoring all the more likely reasons. Googling is only useful if you have a defnite diagnosis from a professional.
Yep a virus, infection, some medicines will all cause a high platelet count according to google. Apparently a virus is very likely to cause a high platelet count in children.
Try try not to worry as if the consultant was really concerned himself he would have taken immediate action rather than just retesting. I know easier said than done! Keep away from google or else you son and the whole family will have some rare tropical disease when you haven't even left the country. Good luck
I'm a doctor (not a paediatrician mind..) and my DS recently had a blood test and his platelet count came back high also. I asked a haematologist I work with and apparently it's perfectly normal for toddlers to have platelet counts up to about 600. Particularly as they often have minor viruses etc that go unnoticed - just their immune systems are active all the time.
Once the rest of his blood test OK should be fine. HTH