Autistic Austin Pledger, who lives in Alabama, began taking anti-psychotic drug Risperdal when he was 8-years-old.
At the time, the Food and Drug Administration had not approved Risperdal for use in children.
More importantly, the drug contained a warning about a low risk for one of its side effects, gynecomastia, which can cause men to grow female breasts.
In 2006, four years after Austin Pledger began using the drug, the FDA approved it as a schizophrenic aid for children.
However they issued new label information that said the drug contained high levels of prolactin, a hormone that promotes breast growth.
But, by this point, Austin had already begun to grow breasts - and now, at 20-years-old, he has reached a bra size of 46DD.
The only way for the young man to have his breasts removed is via mastectomy.
"This trial is important publicly because it provided for the first time a window into the real risks of the drug," Pledger's lawyer Thomas Kline said.
A judge ruled in Austin's favour, insisting that neither the boy nor his family were "adequately warned" about the side effects.
He was awarded $2.5 million - but Janssen Pharmaceuticals, a Johnson & Johnson subsidiary who make Risperdal, have issued a statement expressing disappointment with the judge's decision.
"We firmly believe this verdict should be overturned," the statement read. "Risperdal has improved the lives of countless children and adults throughout the world."
Stock images used throughout.