Psoriasis is a chronic autoimmune disorder affecting the skin that increases the growth rate of skin cells, causing inflamed, itchy, reddened patches with silvery scales, usually on the scalp, elbows, knees, trunk, and back. Psoriasis appears in cycles, with periods of remission followed by flare-ups that can last from weeks to months, and can also be associated with arthritis.
There are several types of psoriasis, including plaque psoriasis, nail psoriasis, guttate psoriasis, inverse psoriasis, pustular psoriasis, erythrodermic psoriasis, and psoriatic arthritis.
Plaque psoriasis – Plaque psoriasis is the most common form of psoriasis, which causes raised, reddened dry skin patches with silvery scales on the scalp, elbows, knees, trunk, and back that may be itchy or sore.
Nail psoriasis – Nail psoriasis appears as abnormal, discolored nails that have pitting (indentations). Severe cases of nail psoriasis may cause nails to detach from the nail bed (onycholysis) or nail disintegration.
Guttate psoriasis – Guttate psoriasis mainly affects children and young adults and is caused by a bacterial infection, such as upper respiratory infections like strep throat, that triggers small, drop-shaped psoriatic patches on the arms, trunk, and legs.
Inverse psoriasis – Inverse psoriasis is characterized by smooth, reddened skin patches in the skin folds of the breasts, groin, and buttocks caused by fungal infections that are worsened by sweating and friction.
Pustular psoriasis – Pustular psoriasis is a rare form of psoriasis that is characterized by generalized patches filled with pus, which usually appear on the palms of the hands and the soles of the feet.
Erythrodermic psoriasis – Erythrodermic psoriasis is the least common type of psoriasis and is characterized by red, peeling rash covering the whole body that itches or burns. This type of psoriasis can be caused by a severe sunburn or taking corticosteroids.
Psoriatic arthritis – Psoriatic arthritis affects the joints, causing stiffness, swelling, and pain that can further cause progressive or permanent joint damage. Psoriatic arthritis affects 10-20% of individuals with psoriasis.