I recently was diagnosed with BFS. Twitching in the right hand to the calves to many other areas of my body. Like you, I have no loss of strength and can walk for miles without issue but have lost weight and my BP fluctuates a lot.
I am not on meds yet and have had MRI’s, EMG’s and CT Scans. So far, nothing conclusive but still have the twitching. It consumes my thoughts which is destructive. I don’t feel myself anymore.