If a man shall have on the skin of his flesh

When discussing the phenomenon of leprosy and the various appearances such a plague could assume, the Torah uses the word adam--man--a term reserved for expressing man’s finest attributes and characteristics. Why doesn’t the Torah use any of the three other Hebrew words for man--ish, gever, or enosh?

The plague of leprosy appeared only “on the skin of his flesh”--on the most external part of a person. Years ago, when G-d afflicted someone with leprosy as a punishment for his deeds, it affected only his most external self, for the inner person was spiritually healthy and not deserving of punishment. Nowadays we have no such phenomenon, as the Biblical leprosy differed form the modern-day disease bearing the same name. In our time, it’s not just the external part of ourselves we must work on and purify. (Sefer Maamarim)