Fifteen-year-old Irish American Keenan Cahill has become an Internet sensation after his video of Katy Perry’s “Teenage Dream” went viral. His lip-synching performance has now racked up over 16 million views.

Keenan Cahill has a rare genetic disorder called Maroteaux-Lamy Syndrome, also known as MPS-VI. Those with the disorder usually stop growing at about age 8 and are characterized by a shortened trunk and restricted movement.

This disorder, which affects one in 25,000 people, has no known cure.

This week  Keenan was a guest of Chelsea Handler, on the “Chelsea Lately Show”, where he did a skit with 50 Cent. Keenan lip-synched “Down On Me” with 50 Cent joining in. This video already as over 4 million viewers although it has only been online for three days.

Altogether he has racked up over 30 million viewers, having laid down tracks such as Usher’s “DJ Got Us Fallin' In Love.”

Cahill said that he has “One day I was going to lunch and someone came up to me and asked if they could get a picture with me – I was like, ‘Ok!’ I’m not going to say no!”