The forms of skin lesions in psoriasis are diverse, with widespread distribution and significant differences in severity. They can be divided into four types:
(1) Plaque Psoriasis
Lesions usually occur on the scalp, trunk, and extensor sides of the limbs. On the skin, red papules appear, gradually enlarging and merging into plaques or patches covered with thick silvery-white scales. The shapes are irregular; some resemble maps or islands, while others present as numerous small lesions scattered like stars across the sky. When the layers of scales fall off and the scales are gently scraped away, a thin red film can be seen underneath. Scraping this red film reveals tiny bleeding points, often referred to as "blood droplets" or medically as punctate bleeding. This is the clinical characteristic of plaque psoriasis.
(2) Pustular Psoriasis
Pustular psoriasis can be generalized or localized. Generalized pustular psoriasis often has an acute onset, with pustules spreading over the entire body within days to weeks. Initially, there are dense, pinpoint-sized, latent small pustules that quickly merge into pus lakes. It is often accompanied by high fever, joint swelling and pain, and general malaise. Blood tests may show increased white blood cells. After the pustules dry up, scaling occurs, followed by new pustules appearing, continuing cyclically.
Localized pustular psoriasis is more commonly seen as palmoplantar pustular psoriasis. Symmetrical red spots appear on the palms and soles, with pinhead to pea-sized pustules forming on them. These typically dry up after about 1-2 weeks, shedding scales, followed by new pustules emerging repeatedly. This type is persistent and stubborn.
(3) Arthropathic Psoriasis
Arthropathic psoriasis is relatively rare and can occur at any age. It can affect both large and small joints simultaneously, but most commonly involves the small joints of the wrists, fingers, and toes. Spinal joints can also be affected.
Affected joints exhibit redness, swelling, and pain. In severe cases, there is fluid accumulation in the joint cavity, and nearby skin swells, limiting movement. Over time, the joints become stiff. In severe cases, X-rays reveal joint destruction. The erythrocyte sedimentation rate (ESR) is elevated, often accompanied by fever and other systemic symptoms. However, rheumatoid factor is negative. In arthropathic psoriasis, skin damage is often accompanied by thick蛎shell-like lesions, or it may only present with the redness and scaling typical of plaque psoriasis.
(4) Erythrodermic Psoriasis
Erythrodermic psoriasis is a more severe and less common form. This type refers to diffuse redness covering more than 70% of the body's skin, with dark red infiltrative skin lesions. Large amounts of bran-like scales cover the surface. Sometimes, due to swelling under the armpits, groin, and around the navel, the epidermis peels off and exudes. The oral mucosa, pharynx, nose, and conjunctiva of the eyes may also become congested and red. Patients often experience fever, chills, headaches, and general discomfort.