There are several different types of PF, the only one I know of that kids grow out of is PFAPA Syndrome (Periodic fever, Aphthous-stomatitis, Pharyngitis, Adenitis)
My daughter has PFAPA her Immunologist said she will probably grow out of it between the ages of 13-17. She is 8 1/2. I have also heard of Adult PFAPA, wher kids had fevers when they were little it went away in teen years, then it came back in there 20's.