Guttate psoriasis on a patient's abdomen. Psoriasis is a condition in which skin cells are produced much faster than normal. The body cannot shed the cells fast enough, resulting in patches (plaques) of scaly, thick skin, which are often itchy and may become infected. Guttate psoriasis causes small lesions (rather than usual large patches in psoriasis) that often follow a streptococcal throat infection.