I had this before a clinical name was attached to it.
I experienced it from about age 10 to about age 38.
It did impair my ability to function in situations where I was had to talk to strangers, and especially a group of strangers.
It impaired my ability to contribute to meetings at work, and to work well with co-workers.
I avoided social gatherings at all costs, and avoided people at gatherings that I could not avoid.
I joined Toastmasters and that fixed the problem after a few years.
For me, that was the miracle cure.
I'm still quite shy, mind you, and I still feel anxiety at times, but now I have the confidence and the mental tools to make the anxiety work for me instead of against me.
Now I often seek out those who are trying to fade away from the crowd, strike up conversation, and try to make them feel more at ease.
Speak to a crowd of strangers? Take center stage? No problem now.
Toastmasters is an incredibly cheap and effective treatment for this condition.
I recommend it highly.