 During his time at UCLA, he created mouse models to observe the effects of mutations on genes linked to sexual development.In 1999, Vilain was the first geneticist to describe IMAGe syndrome, a rare and severe congenital disease, and in 2012, identified its causative mutations.In 2005, he was one of the pediatricians present at the International Consensus Conference on Intersex in Chicago, to advocate for the term “disorders of sex development.” He also worked with intersex advocate Bo Laurent to remove the term “hermaphrodite” from the medical vocabulary.