Leigh has osteonecrosis, which is essentially when there's a death of bone tissue because of inadequate blood supply to the area, according to the Mayo Clinic. As a result, Leigh uses a cane for support.

The Shadow and Bone author has been refreshingly candid on social media about her real-life fears regarding her diagnosis.

In one Twitter post from 2020, Leigh wrote, "Headed in for MRI today to check the progress of my osteonecrosis. I put it off for a long time because I just didn't want to know and I'll admit to being pretty scared. Good thoughts are welcome."

According to the Cleveland Clinic, there isn't a known cure for osteonecrosis.

Leigh revealed in an Instagram post from 2015 that Kaz's use of a cane was inspired by her own journey living with osteonecrosis.