Transcript for Rare Ailment Forces High School Basketball Star to Tan
medical mystery we've been talking about. A high school basketball star with a disease, so require that doctors don't know what causes it or how to cure it. But they know what helps, going to the tanning salon off that basketball court. Linsey davis is here with more. Reporter: Josh borrelli is the golden child. The senior with the deep tan in the midst of winter. He sports a tan that is prescribed. The ultraviolet rays are so protective, he can't miss a day without tanning. Without it, the disease with life-threatening complications could resurface. 19 seconds left in the game. Shawnee is down by one. That's when they give it to josh borrelli. The guy on the team with the most experience at overcoming adversity. Borrelli has a rare auto immune disease called mucha hagerman. I had red lesions all over my body. I went to the doctor. It was the first or second case he had seen in his 40-year practice. Reporter: After eighth grade, the disease went into remission. Until just weeks before the start of his senior season. The lesions came back. And the doctor described medication and daily visits to the tanning salon. My dad went with me the first couple times because I was nervous. Reporter: At the time, he wasn't just believed to be the only person in the state of new jersey with the disease, but the country. A disease with no known cause or cure. This disease is so rare, that most dermatologists don't see it in their entire practice. Reporter: Many people confuse with chickenpox and think it's contagious. But it's not. It's very challenging for him. But I've seen him rise to the occasion. Reporter: Eight minutes a day in a tanning salon helps to keep sease at bay. So, the only thing that looks different about his skin right now is his copper tone complex. Other than that, everything about his look is smooth. Including his jump shot. Moves like that will play to fans, fear the tan t-shirt. If anything, it's helped it. There's people out there worse off than I am. I know I'm really lucky. Reporter: Borrelli averages 20 points a game. He's 2 points shy of 1,000 points in his career. Right now, all is well. But the doctor says the disease could resurface. It can come and go for years at a time.
This transcript has been automatically generated and may not be 100% accurate.