Honestly, Did You Ever Think You’d See the Word “Vitiligo” in Here?By Rabbi Jack Abramowitz
A bald patch in the hair or beard is a sign of tzaraas if the discoloration goes beneath the surface and there are thin yellow hairs in it. If the discoloration is only on the surface, but there are no healthy black hairs in it, the kohein will quarantine the person for a week, then re-examine him. If the affected area hasn’t changed, and there are still no yellow hairs in it, the person must shave himself, but not the area in question. The kohein will then quarantine him for another week.
After the second week, if things still haven’t worsened, the kohein will declare the person clean and the person immerses himself and his clothes in a mikvah. However, if the discoloration increases after this, he’s automatically impure, even if the yellow hairs never appeared. (If black hairs grow there, he’s clean.)
If a person develops dull white spots all over, that’s not tzaraas. It’s a rash, or maybe vitiligo, but the person is ritually clean.