I'm a Japanese man who may have suffered from selective mutism about 10 years. When I couldn't speak at school, I didn't see any specialists. So, to my regret, I can't fully evaluate whether I was a selective mute child or not.
The first time I became mute was when I was 9 years old. My words didn't come out when I changed my school. It may be odd, because it is known that selective mutism mostly manifest itself when children enter kindergarten or school. But according to a study, selective mutism develop even after puberty in rare cases.
When I graduated from college, I was still too shy. I couldn't get a job.
Right now I spend my time managing my blog The Selective Mutism Journal written in Japanese aimed at introducing the latest findings about Selective Mutism from US, Canada or UK into Japan. In addition, I learn how to earn income every day. Of course, I study English every day. :)