Thanks for the query,
You are very true in saying that there is no definitive treatment for premature greying.
A few products like PABA and melatonin
are of some use.
Regarding the cause, You very well know, the genes has to be blamed :)
Till now no definitive cause is known.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.