Psoriasis vulgaris, Koebner phenomenon. Well-delineated erythematous plaque with a silvery-white scale characteristic of psoriasis. Slideshow: Common Childhood Skin Problems: From Rashes to Ringworm Slideshow: What Your Skin Says About Your Health. More From WebMD: Hemophilia Treatment RA Basics Psoriasis MS Assessment Hemophilia Questions Anaphylaxis ADHD in Children Diabetes Diet Hodgkin’s Lymphoma Multiple Myeloma Breast Cancer Toenail Fungus Living With Alzheimer’s COPD Prostate Cancer Clinical Trials Idiopathic Pulmonary Fibrosis Diabetes Assessment Live Better With Diabetes Atrial Fibrillation Assessment Treating Advanced Prostate Cancer. There are five types of psoriasis, yet people most often have only one type of psoriasis at a time. Plaque psoriasis (also called psoriasis vulgaris) is the most common form. The commonest form of psoriasis is plaque psoriasis in which patients may have sharply circumscribed, round-oval, or nummular (coin-sized) plaques (fig 2).
Psoriasis is more common with certain human leukocyte antigen (HLA) subtypes, but these cannot be distinguished histologically or clinically and there is no apparent difference in the response to therapy. In mild psoriatic disease, where 1 or 2 plaques are resistant to topical treatments, for example, intralesional steroids may play a role.