"My doctor says it's abnormal but can't officially link it to any known medical conditions."
He already has unusually long fingers, so when he extends his thumb it "looks crazy" to others.
"It's weird on my hand," Mr Pina told Boston.com. "It's out of place. All my fingers are long, so when I stretch out my hand it kind of looks normal. But when I stick it up, it looks crazy."
Extending his thumb is painless, and has earned him millions of views on TikTok, where he shares video of his unusual trait.
"When I posted my first video to TikTok, I had no clue I'd get this sort of attention from it. People have mixed reactions, like disgusted, freaked out, or curious," Mr Pina told Buzzfeed.
He jokes that it's his "useless superpower" and uses TikTok to answers questions like: "Why are you not the world thumb-wrestling champion???"
Mr Pina also has shown off his green thumb and hitchhiking abilities.
His videos have attracted thousands of comments, with people mystified by his thumb, which many believe "can't be real".
"How is this guy mutating his thumb to become longer and scientists are not taking his DNA," one person wrote, while another added: "It is weird that I want to see his thumb grow while under an X-ray or something."
"But like how does your finger fix itself," another asked.
