That's what doctors would like to know.
Shanyna Isom was studying criminal justice at the University of Memphis when an allergic reaction to a steroid treatment for an asthma attack cut her dreams short. Isom subsequently developed a condition that causes her hair follicles to produce skin cells at 12 times the normal rate.
That was two years ago, and doctors are still not entirely sure what's causing the debilitating skin disease.
With the help of specialists at Baltimore's Johns Hopkins, Isom was able to control the symptoms. "I couldn't sit up I couldn't walk," she told WMC-TV. "Now I can walk with a cane and sometimes I can walk on my own."
But the treatment, which includes taking 17 different medications, is expensive, and Isom's in-state insurance doesn't cover her out-of-state expenses. She turned to family and friends and various fundraisers to help pay off her medical bills, but Isom still owes hundreds of thousands of dollars.