How does a male get genital psoriasis if he has never really had it before?

Psoriasis: Psoriasis is a chronic skin disorder that affects 1% to 3% of the world's population. It is characterized by periodic flare-ups of well defined, red patches covered by a silvery, flaky scale on the extensor surfaces and the scalp. Causes include genetics, stress, medications, skin injury, immune system dysfunction, low levels of calcium and others.