What Could The Shin "spot" Be?

A colleague and good friend of mine has a 5 year old son, African American, who has had unusual episodes recently of suddenly falling while walking or running and some leg pain. Upon the initial xray, there was nothing to note. 3 weeks later there was a "spot" on the xray in the shin area. He has to go for an MRI soon. I'm just trying to prepare myself for what may lie ahead or how I can best support my friend.