Selective mutism is a severe anxiety disorder which leaves the sufferer unable to speak in certain situations.
DD is the loudest mute child I know.
She has had SM since she was a baby. At age 2 she would only speak to me. Now at 7 she can speak to all of the family and she's able to speak in school unless it's a substitute teacher. She knows all of the teachers and TAs.
She's gone from silent and tracking behind academically to talkative and perfectly average and in some subjects she's even ahead of what's expected. To say I'm proud of her is an understatement.
We still have work to do, she can't speak to shop keepers, some people in public, bus drivers etc, but she's made such immense progress.