Alopecia Areata and Alopecia Barbae
A nega in the beard or hair, called a nethek נתק, may be what is commonly known as AA or Alopecia areata.
The nethek is a bald patch (not caused by hair picking or shaving) the size of a griss, that may be indicative of immediate tumah, provided that it has at least two thin golden-colored hair strands in that bald patch area.