Hi Christina
Welcome to NeuroTalk

.
I am sorry to read about your son.
It is possible that his doctors suspect what is called Sydenham's Chorea - it usually arises from a Streptococcal infection.
The information in these two sites might help you to ask his doctors informed questions.
Sydenham's Chorea
- AboutKidsHealth
Sydenham's chorea - Gillberg centrum, University of Gothenburg, Sweden
All the best.