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There are five main types of skin psoriasis, plus psoriatic arthritis — which affects the joints. Doctors identify psoriasis types by the symptoms they present. It is possible to have multiple types of skin psoriasis at one time, or one type of psoriasis may change into another type of psoriasis. It is possible to have psoriatic arthritis alone or with skin psoriasis.
The most common type of psoriasis, plaque psoriasis, makes up 80 percent of psoriasis cases. Plaque psoriasis, also called psoriasis vulgaris, typically affects the elbows, knees, back, and scalp, but may appear elsewhere. Plaque psoriasis is characterized by patches (plaques) of thick, reddened, patches of skin that can crack or bleed where the skin bends at joints. Plaques are often covered with white or silver scales. Plaques cause intense itching, burning, and soreness.
Topical treatments alone may not be effective for plaque psoriasis, but usually are the starting point of treatment. Oral or injected immunomodulating drugs may be necessary to control severe or widespread cases.
In guttate psoriasis, patches of rash are small and scaly, and have a round, oval, or teardrop shape. Lesions may look red or pink on people with pale skin and darkened on people with darker skin. Guttate psoriasis can affect any part of the body except the palms of the hands and soles of the feet, but commonly it is confined to the arms, legs, chest, and scalp. Guttate psoriasis causes itching in some people.
Guttate psoriasis is most common in childhood, adolescence, and early adulthood. Some people experience recurrent bouts of guttate psoriasis, but others only have one episode that never repeats. Bouts are often triggered by an infection, often a streptococcal infection such as strep throat. Topical treatments are usually effective for controlling guttate psoriasis, but it may also respond to phototherapy or systemic medications.
Also called flexural or intertriginous psoriasis, inverse psoriasis causes smooth patches of skin that are red or darkened in color and feel painful. The characteristic silvery scale of psoriasis is often not seen in this form. Inverse psoriasis is more common in overweight people, and usually appears in areas where sweat and friction occur from skin rubbing against skin — such as the armpits, genitals, and under the breasts.
Treatment of inverse psoriasis can be challenging because the areas are so sensitive, and medication absorbs more effectively, making side effects more likely. Some treatments that work for other types of psoriasis tend to irritate inverse psoriasis. It is often misdiagnosed as fungus, as it can look like jock itch.
Pustular psoriasis, an uncommon form of the disease, causes intensely red or darkened skin with sterile pus-filled blisters. The skin around the blisters may be prone to cracking. The blisters can burst, leaving crusty skin. There are two subtypes of pustular psoriasis. Palmoplantar pustulosis (PPP), also called acropustulosis, is limited to the palms of the hands and soles of the feet. Generalized pustular psoriasis (GPP), also referred to as von Zumbusch psoriasis, is widespread. Pustular psoriasis is very painful and can be debilitating. In particular, GPP can be life-threatening and requires urgent medical treatment and may require hospitalization.
Pustular psoriasis can occur at any age. Flares can come on rapidly and be accompanied by fever and malaise. Pustular psoriasis can be difficult to treat and prone to flares. If topical treatment fails, systemic treatment such as Methotrexate or Cyclosporine may be required. Psoralen + UVA (PUVA) treatment can also be helpful.
Erythrodermic psoriasis, also called exfoliative psoriasis, is the rarest type of psoriasis. This highly inflammatory form can affect the whole body, causing a bright red rash that itches, burns, and peels off in sheets. Skin affected by erythrodermic psoriasis can look as though it has been burned. Approximately 3 percent of people with psoriasis experience a bout of erythrodermic psoriasis at least once during their lives. Erythrodermic psoriasis may accompany a flare of generalized pustular psoriasis.
Other symptoms include increased heart rate, difficulty controlling body temperature, shivering, and edema (swelling) — especially in the ankles. Erythrodermic psoriasis can be life-threatening and necessitates immediate medical treatment and hospitalization. Treatment usually involves a combination of one or two systemic immunomodulators with a topical medication.
Psoriatic arthritis (PsA) can cause inflammatory pain, swelling, and progressive damage in any joint in the body. Researchers estimate that between 15 percent and 30 percent of those with skin psoriasis will develop psoriatic arthritis. It is possible to have psoriatic arthritis without skin psoriasis.
There are three subtypes of psoriatic arthritis:
It is possible to have more than one subtype of PsA.
Typically, psoriatic arthritis develops between the ages of 30 and 50, but it can occur earlier, even in children. Treatment of psoriatic arthritis includes pain management as well immunosuppressive medications that halt the progression of joint damage.