• Plaque (or common) psoriasis. Well-defined red patches, round or oval, covered with thick crusts of white skin which flaky. Usually located on the elbows, knees, scalp and buttocks. These plaques can cause discomfort, pain and sometimes intense itching.
• Psoriasis of the nails. Various abnormalities of the fingernails and toenails: small “depressions” that look like thimble holes, peeling, crumbling, discoloration, thickening, streaks.
• Scalp psoriasis. Red patches with silvery scales on the scalp and the edge of the forehead.
• Palmoplantar psoriasis. Dry patches on the palms of the hands and the soles of the feet, often painful and cracked.
• Reverse (or invert) psoriasis. Red plaques that appear in the folds (in the armpits, groins, near the genitals, in the folds of the buttocks), without scales, and sometimes painful since exposed to friction.
• Pustular psoriasis. Plates covered with small white pustules, especially on the hands and the sole of the foot (palmoplantar pustulosis). This shape can also touch the fingertips.
• Erythrodermic psoriasis. Almost all of the skin is red and inflamed, with no specific patches. There is often a fever and chills. It is a serious form, which requires urgent treatment.
• Guttate psoriasis. Rare form that mainly affects children and adolescents and occurs after streptococcal infection (tonsillitis or pharyngitis, most often). The plaques are small (less than 1 cm), teardrop shaped, and are often present on the trunk, arms and legs.

Notes. You cannot spread the plaques to other people or spread them elsewhere on your own body. They are not contagious.