These skin problems can look alike at the skin surface, but they're different under a microscope. The rash pattern of guttate psoriasis looks like parapsoriasis and also shows up on your chest, but it tends to come on after an infection. The plaque form of psoriasis may look like parapsoriasis when you first notice it, but it eventually becomes thick patches of flaky skin, usually on your knees, elbows, scalp, and lower back.