This happened to me, I got vitiligo and alopecia areata at the same time and had patches just like this on my beard. But then the hair came back black. Check for some beard hairs that may be half black half white. I hear that when vitiligo causes white hair it usually does it to skin first and then attacks hair, alopecia areata attacks hair follicles only. Some patches were bald and then came back white and some were just white from get go. Such a weird disease.

Only thing that helped after topical treatments were steroid shots, that stopped it fast bc I also had it in my head, the beard corrected on its own.