Types of Psoriasis Overview
Psoriasis is a chronic disease of the skin that affects approximately 5.5 million people in the United States. Typical psoriasis appears as red, dry, elevated plaques of skin. There are other less common clinical forms of psoriasis. Psoriasis is not contagious and is often inherited. A brief overview of each type of psoriasis is provided below.
Plaque-type psoriasis is the most common type of psoriasis. Approximately, nine out of 10 people with psoriasis have plaques. The disease begins with a small scaling red bump that coalesces with other similar bumps to form an elevated plaque of red skin that is covered with silvery scales. Circular- to oval-shaped red plaques that sometimes itch or burn are typical of plaque psoriasis. The plaques usually are found on the elbows, knees, trunk, or scalp, but they may be found on any part of the skin. Most plaques of psoriasis are persistent (they stay for years and do not tend to come and go).
Picture of plaque psoriasis on a leg. Image courtesy of Hon Pak, MD. Picture of plaque psoriasis on an abdomen. Image courtesy of Hon Pak, MD.
Guttate psoriasis looks like small salmon-pink (or red) bumps on the skin. The word guttate is derived from the Latin word gutta, meaning drop. Usually, a fine scale surmounts the drop-like lesion that is much finer than the scales in plaque psoriasis. Guttate psoriasis usually occurs on the trunk, arms, or legs. However, it may cover a large portion of the body. This type of psoriasis often "runs its course" and may even go away without treatment in a few weeks. Sometimes guttate psoriasis can be more persistent, and it may evolve into plaque psoriasis.
Picture of guttate psoriasis. Red drop-like lesions are found on the skin. Image courtesy of Hon Pak, MD. A close-up view of guttate psoriasis. Notice the salmon-pink (red) drop-like lesions. Fine scales can be seen on the lesions. These scales are much finer than those associated with plaque psoriasis. Image courtesy of Hon Pak, MD.
The guttate form of psoriasis is the second most common form of psoriasis. About 2% of those with psoriasis have the guttate type. This type of psoriasis is more common in children and adults younger than 30 years of age.
The trigger to the disease is often a streptococcal bacterial throat infection. The eruption of the lesions on the skin usually occurs two to three weeks after a streptococcal sore throat. Outbreaks may resolve only to return with the next strep throat.
Psoriasis Symptoms and Signs
Plaque psoriasis, the most common form, usually produces plaques of red, raised, scaly skin affecting the scalp, elbows, and knees. The plaques may itch or burn.
The flare-ups can last for weeks or months. Psoriasis can spontaneously resolve only to return later (chronic).
Pustular psoriasis is an uncommon form of psoriasis. People with pustular psoriasis have clearly defined, raised bumps on the skin that are filled with pus (pustules). The skin under and around these bumps is reddish. Pustular psoriasis may cause large portions of the skin to redden. Pustular psoriasis can occur alone or with plaque-type psoriasis.
Picture of pustular psoriasis. Image courtesy of Hon Pak, MD. Picture of pustular psoriasis. Image courtesy of Hon Pak, MD.
Pustular psoriasis is classified into one of several types, depending on the symptoms. The lesions may be come on suddenly (acute) or be long-term (chronic), or somewhere in between (subacute). Extensive pustular psoriasis (von Zumbush) often has systemic effects producing acute symptoms like fever, chills, nausea, headache, and joint pain. Pustular psoriasis can be so severe that it requires hospitalization. Pustular psoriasis of the palms and soles is usually chronic and has red patches studded with white to yellow pustules. A ring-shaped (annular, or circinate) type also exists. It is usually subacute or chronic, and people with this type do not usually have symptoms aside from the skin symptoms. Acrodermatitis continua is a rare type of pustular psoriasis that involves the fingertips. Fingernails may accumulate lakes of pus over the nail bed. The lesions may be very painful and result in permanent nail destruction.
Bright red, smooth (not scaly) plaques are found in the skin folds (intertriginous areas). The most common areas are under the breasts, in the armpits, near the genitals, under or between the buttocks, or in abdominal folds. These irritated and inflamed areas are aggravated by the sweat and skin rubbing together in the folds. Yeast overgrowth may trigger the skin lesions of psoriasis.
Topical creams and ointments are used to treat inverse psoriasis. Corticosteroids, vitamin D3 derivatives, topical retinoids, coal tar, tacrolimus, or anthralin have been used. Due to the sensitive nature of the skin in the folds of the body, irritation from treatment is common. Another problem is that these moist irritated areas can be prime areas for yeast and other fungal infections.
This is the least common type of psoriasis and can be quite serious. A very large area of the skin becomes bright red, inflamed, and scaly. The entire skin surface can appear to be covered in a red, peeling rash. The rash usually itches or burns. The increased blood flow can even sometimes put a strain on the heart.
Topical and systemic medications may be used to treat erythrodermic psoriasis. Sometimes people with this type of psoriasis become prone to dehydration, congestive heart failure, infection, and fever.
Nail psoriasis can affect the fingernails and toenails.
Picture of nail psoriasis of the fingernails and toenails. Note the discoloration. Image courtesy of Hon Pak, MD.
Most, but not all, people who have psoriasis of the nails also have skin psoriasis (also called cutaneous psoriasis or simply psoriasis). Psoriasis of the nails occurs in fewer than 5% of people who do not have skin psoriasis. In people who have skin psoriasis, 10%-55% have psoriasis of the nails (also called psoriatic nail disease). About 10%-25% of people who have skin psoriasis also have psoriatic arthritis, a specific condition in which people have inflammation of both the joints and the skin. Of people with psoriatic arthritis, 53%-86% have affected nails.
Psoriasis of the nails can cause a number of changes to the nail area. Clear yellow-red nail discoloring that looks like a drop of oil under the nail plate may occur. Little pits may form in the nails. These pits develop when cells are lost from the nail's surface.
Picture of nail psoriasis with pitting. Image courtesy of Hon Pak, MD.
Lines may develop going across the nails (side to side rather than root to tip). Areas of white on the nail plate may also be present.
The skin under the nail may thicken and lead to loosening of the nail. A white area may develop under the tip of the nail where it is separated from the skin underneath. This usually starts at the tip of the nail and extends toward the base. The nail may weaken and start to crumble because the underlying structures are not healthy. The pale arched area at the bottom of the nail may become red. This occurs when the capillaries under the nail are congested.
Nail psoriasis can also occur with fungal infections of the nail (onychomycosis) and inflammation of the skin around the edges of the nail (paronychia).
Psoriasis of the nails is not contagious.
Psoriasis of the Scalp
The scalp may have fine dry scaly skin or have heavily crusted plaque areas. The plaque can flake off or peel off in crusted clumps. Sometimes psoriasis of the scalp is confused with seborrheic dermatitis.
Picture of psoriasis of the scalp. Image courtesy of Hon Pak, MD.
Medicated shampoos are used to loosen the scales from the scalp. Salicylic acid and coal tar are used as active ingredients in psoriasis shampoo. Topical or systemic medications may be used to treat the psoriasis.
When psoriasis involves the palms and/or the soles, special problems occur. Since these surfaces are often extremely important in our normal activities, significant involvement can be debilitating. Because the skin in these area is so thick naturally, treatment with topical medication may not be adequate and alternative treatments must be considered.
Psoriatic arthritis is a disease in which a person may have both psoriasis and inflammatory arthritis. Psoriatic arthritis is a potentially destructive and deforming form of joint disease.
Picture of severe psoriatic arthritis involving the finger joints.
Psoriatic arthritis, like psoriasis, is an autoimmune disease, meaning that the immune cells damage one's own tissues. Rarely, a person can have psoriatic arthritis without having skin psoriasis. Usually, the more severe the skin symptoms are, the greater the likelihood a person will have psoriatic arthritis.
Picture of psoriatic arthritis. Severe deformity of the joints at the ends of the fingers.
Psoriatic arthritis affects 10%-30% of people with psoriasis. A recent survey by the National Psoriasis Foundation indicated that approximately 1 million people in the United States have psoriatic arthritis. Often people who have psoriasis are unaware that they have psoriatic arthritis.
Systemic Disease in Psoriasis
It is important to recognize that patients with psoriasis are predisposed to a number of systemic conditions that can adversely impact their general health, including obesity, diabetes, and cardiovascular disease. It seems that the inflammatory process is not limited to the skin. These diverse problems are sometimes lumped together as "metabolic syndrome." It is often prudent for all psoriasis patients to be closely followed by their primary-care doctors as well as their skin specialist.