The term that we use in child psychiatry and child psychology is selective mutism.
From the abcnews.go.com
The team is conducting trials in China, where antibiotic deaf-mutism is widespread.
From the newscientist.com
A trained therapy dog named Puppy eventually broke the back of her selective mutism.
From the stltoday.com
He was diagnosed with cerebellar mutism and has had to relearn how to walk and speak.
From the news-journalonline.com
Mutism is absence of speech with apparently normal level of consciousness.
From the en.wikipedia.org
Just a little attention and love helped her overcome her mutism in minutes.
From the blogs.psychcentral.com
Purvis says selective mutism has been recognized since the late 1800s.
From the kansas.com
The condition, called selective mutism, is a symptom of a larger social anxiety disorder.
From the washingtonpost.com
After being in a coma for three weeks, she developed akinetic mutism.
From the stltoday.com
More examples
The condition of being unable or unwilling to speak; "her muteness was a consequence of her deafness"
Muteness or mutism is a kind of speech disorder that causes an inability to speak. The term mute originates from the latin word mutus, for silent.
A psychological disorder in which the sufferer cannot speak in certain situations
Unable to speak, inarticulate; inability or refusal to speak.
Inability to produce any verbal utterance; may be due to disordered language, speech, or voice
The inability or unwillingness to speak. A person who is mute cannot or does not care to talk. Someone who was mute was said to be dumb, not in the sense of being stupid, but in the sense of being devoid of the power of speech. ...
Inability to speak due to conscious refusal or psychological inhibition.