There are five official types of psoriasis – plaque psoriasis, guttate psoriasis, pustular psoriasis, inverse psoriasis, and erythrodermic psoriasis – as well as some additional subtypes. Plaque psoriasis is by far the most common, occurring in approximately 80 percent of people with psoriasis, followed by guttate psoriasis which affects about 10 percent of sufferers. While most types of psoriasis result from the same triggers such as stress, weather, medications, diet, and infections, the symptoms and treatment plans differ from one type to the next.
Plaque psoriasis, otherwise known as psoriasis vulgaris, is characterized by red patches of skin that are usually covered by a white scaly layer of dead skin cells. They are typically 1 to 10 centimeters wide and are most often found on the elbows, knees, lower back, and scalp. Symptoms tend to get worse with scratching and may last for weeks, months, or even years.
Guttate psoriasis is characterized by small teardrop-shaped lesions on the torso and limbs, but spots can also appear on the face and scalp. They are often triggered during childhood or young adulthood, following a period of stress, strep throat, skin injury, infection, or medication. The spots are usually less thick than those of plaque psoriasis, but sometimes they develop into plaque psoriasis over time.
Pustular psoriasis is characterized by white pustules surrounded by red skin. It is a severe type of psoriasis accompanied by cyclic periods of pustules and remission. Pustules are often found on isolated regions of the body, such as the hands and feet, and develop very rapidly. In some cases, the pustules join together and form scaling. In other cases, flu-like symptoms occur, including fever and chills, rapid pulse, loss of appetite, and muscle weakness. There are three forms of pustular psoriasis – von Zumbusch, palmoplantar pustulosis (PPP), and acropustulosis – with varying symptoms and severity.
Inverse psoriasis, or flexural psoriasis, is characterized by shiny and smooth red lesions in the folds of the body. These skinfolds include behind the knees, under the breasts, in the armpits, and around the groin area. The moist environment of such skinfold regions prevents scales from forming and as such, this type is commonly mistaken for fungal and bacterial infections. Moreover, due to the skin-on-skin contact experienced with inverse psoriasis, it is more common in overweight individuals and can be very uncomfortable.
Erythrodermic psoriasis, otherwise known as exfoliative psoriasis, is characterized by red and scaly patches on large portions of the body. These patches may look like severe burns and can develop from a bad sunburn, an infection, alcoholism, significant stress, or poorly managed plaque psoriasis. People with erythrodermic psoriasis may require hospitalization if the body becomes unable to control its temperature, which can quickly turn into a medical emergency.
Regardless of type, psoriasis is never contagious and is only life-threatening in its most severe form. The majority of people will only have one type at a time, but it is possible to have two different types together, or one form that develops into another. Between 10 and 30 percent of people with psoriasis will also develop psoriatic arthritis, a painful and physically limiting condition of the joints. This is due to the fact that psoriasis triggers the body to attack both the joints and the skin.