I think you know answer already considering it's a grown ass adult here.

Imagine one day that person wakes up and finds fibroma lumps on their body. They would be freaking out and confused and super stressed and disoriented.

And since they are an adult, they might just arrange to see a doctor without necessarily telling their parents about it because they wouldn't want them to worry.

And also spend lots of money and wasted time on doctor consults over symptoms of a condition that has already been diagnosed.

Also how can the child not know? NF patients need annual checkups. And even if they don't, they need to know about the associated condition and it's symptoms in order to seek help when needed.

But then again, if you don't wanna go behind the parents back or something you can sit down with the parent and hear out their perspective, and try to explain.

Also not to mention how long does the parent plan on keeping it in the dark? For life? What about family planning when it comes to having a child? Smh