TT #125 · Parshas Tazria · Aliyah 2 · Passuk 10
English: If the eruption spreads out in the skin, so that the eruption covers all the skin of the affected person from head to foot, as far as the priest can see,
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:12
Torah Temimah cites Sifra (Toras Kohanim) for excluding a mere bright spot from the rule for a full-body eruption.
Sifra — Vayikra 13, Midrash Sefer
English: “The eruption covers” excludes a mere bahak, a non-tzaraas discoloration.
Textual derivation
A bright spot that is not classified as tzaraas does not count as the eruption described in the full-body rule.