וְאִם־פָּשֹׂ֥ה תִפְשֶׂ֖ה בָּע֑וֹר וְטִמֵּ֧א הַכֹּהֵ֛ן אֹת֖וֹ נֶ֥גַע הִֽוא׃
And if it spread abroad in the skin, then the priest shall pronounce him unclean: it is a plague.
Read kabbalistic (mystical) interpretation of Leviticus 13:22: and classical mystical sources.