Various forms of psoriasis exist. Some can occur alone or at the same time as other types, or one may follow another. The most common type is called plaque psoriasis, also known as psoriasis vulgaris.
Plaque psoriasis leads to skin patches that start off in small areas, about one-eighth of an inch wide. They usually appear in the same areas on opposite sides of the body.
The patches slowly grow larger and develop thick, dry plaque. If the plaque is scratched or scraped, bleeding spots the sizes of pinheads appear underneath. This is known as the Auspitz sign.
Some patches may become ring shaped (annular), with a clear center and scaly raised borders that may appear wavy and snake-like.
As the disease progresses, eventually separate patches may join together to form larger areas. In some cases, the patches can become very large and cover wide areas of the back or chest. This is known as geographic plaques because the skin lesions resemble maps.
Plaque psoriasis may persist for long periods of time. More often it flares up periodically, triggered by certain factors such as cold weather, infection, or stress.
Patches most often occur on the:
They may also be seen on the:
Psoriasis of the scalp affects about 50% of patients. In some cases, the psoriasis may cover the scalp with thick plaques that extend down from the hairline to the forehead.
Psoriasis patches rarely affect the face in adulthood. In children, psoriasis is most likely to start in the scalp and spread to other parts of the body. Unlike in adults, it also may occur on the face and ears.
Less Common Forms of Psoriasis
Description of Skin Patches
The patches are teardrop-shaped and appear suddenly, usually over the trunk and often on the arms, legs, or scalp. They often disappear without treatment.
Guttate psoriasis can occur as the initial outbreak of psoriasis, often in children and young adults 1 - 3 weeks after a viral or bacterial (usually streptococcal) respiratory or throat infection. A family history of psoriasis and stressful life events are also highly linked with the start of guttate psoriasis.
Guttate psoriasis can also develop in patients who have already had other forms of psoriasis, most often in people treated with widely-applied topical (rub-on) products containing corticosteroids.
Patches usually appear as smooth inflamed areas without a scaly surface. They occur in the folds of the skin, such as under the armpits or breast, or in the groin.
Inverse psoriasis may be especially difficult to treat.
Patches appear as red scaly areas on the scalp, behind the ears, above the shoulder blades, in the armpits or groin, or in the center of the face.
Seborrheic psoriasis may be especially difficult to treat.
Tiny white pits are scattered in groups across the nail. Toenails and sometimes fingernails may have yellowish spots. Long ridges may also develop across and down the nail.
The nail bed often separates from the skin of the finger and collections of dead skin can build up underneath the nail.
Over half of patients with psoriasis have abnormal changes in their nails, which may appear before other skin symptoms. In some cases, nail psoriasis is the only symptom.
Generalized Erythrodermic Psoriasis (also called psoriatic exfoliative erythroderma)
This is a rare and severe form of psoriasis, in which the skin surface becomes scaly and red. The disease covers all or nearly all of the body.
About 20% of such cases evolve from psoriasis itself. The condition may also be triggered by certain psoriasis treatments, and other medications such as corticosteroids or synthetic antimalarial drugs.
Patches become pus-filled and blister-like. The blisters eventually turn brown and form a scaly crust or peel off.
Pustules usually appear on the hands and feet. When they form on the palms and soles, the condition is called palmar-plantar pustulosis.
Pustular psoriasis may erupt as the first occurrence of psoriasis, or it may evolve from plaque psoriasis.
A number of conditions may trigger pustular psoriasis, including infection, pregnancy, certain drugs, and metal allergies.
Pustular psoriasis can also accompany other forms of psoriasis and can be very severe.
Psoriatic arthritis (PsA) is an inflammatory condition that leads to stiff, tender, and inflamed joints. Estimates on its prevalence among those with psoriasis range from 2 - 42%. AIDS patients and those with severe psoriasis are at higher risk for developing PsA.
About 80% of PsA patients have psoriasis in the nails. Arthritic and skin flare-ups tend to occur at the same time. It is not clear whether psoriatic arthritis is a unique disease or a variation of psoriasis, although evidence suggests they are both caused by the same immune system problem.
Although patients with psoriatic arthritis tend to have mild skin symptoms, the disease affects the entire body. PsA, therefore, is more serious than the more common plaque psoriasis. Infrequently, the course of PsA has been associated with a syndrome known by the acronym SAPHO, which stands for:
Some experts group PsA into five forms. The forms differ according to the location and severity of the affected joint:
People who start to smoke after developing psoriasis may delay the onset of psoriatic arthritis. However, research has also linked smoking to an increased risk of psoriasis, and because smoking causes serious health problems and should not be considered as a way to delay this type of psoriasis.
Chen YJ, Wu CY, Shen JL, Chu SY, Chen CK, Chang YT, Chen CM. Psoriasis independently associated with hyperleptinemia contributing to metabolic syndrome. Arch Derm. 2008;144:1571-1575.
Gelfand JM, Neimann AL, Shin DB, et al. Risk of myocardial infarction in patients with psoriasis. JAMA. 2006 Oct 11;296(14):1735-41.
Kurd SK, Gelfand JM. The prevalence of previously diagnosed and undiagnosed psoriasis in US adults: Results from NHANES 2003-2004. J Am Acad Dermatol. 2008 [Epub ahead of print].
Leonardi CL, Kimball AB, Papp KA, Yeilding N, Guzzo C, Wang Y, et al. Efficacy and safety of ustekinumab, a human interleukin-12/23 monoclonal antibody, in patients with psoriasis: 76-week results from a randomized, double-blind, placebo-controlled trial (PHOENIX 1). Lancet. 2008;371:1665-1674.
Liu Y, Helms C, Liao W, Zaba LC, Duan S, Gardner J, et al. A genome-wide association study of psoriasis and psoriatic arthritis identifies new disease loci. PLoS Genet. 2008;4(3):e1000041.
Menter A, Gottlieb A, Feldman SR, Voorhees ASV, Leonardi CL, Gordon KB, et al. Guidelines for the management of psoriasis and psoriatic arthritis. J Am Acad Dermatol. 2008;5:826-850.
Menter A, Griffiths CE. Current and future management of psoriasis. Lancet. 2007;370:272-284.
Paller AS, Siegfried EC, Langley RG, Gottlieb AB, Pariser D, Landells I, et al. Etanercept treatment for children and adolescents with plaque psoriasis. N Engl J Med. 2008;358:241-251.
Papp K, Bissonnette R, Rosoph L, Wasel N, Lynde CW, Searles G, et al. Efficacy of ISA247 in plaque psoriasis: a randomized multicentre, double-blind, placebo-controlled phase III study. Lancet. 2008;371:1337-1342.
Stern RS. Psoralen and ultraviolet A light therapy for psoriasis. N Engl J Med. 2007;357:682-690.
U.S. Food and Drug Administration. CDER Drug and Biologic Approvals for Calendar Year 2006 -- Updated through August 31, 2006. Last accessed on 15 October, 2006.
Weatherhead S, Robson SC, Reynolds NJ. Management of psoriasis in pregnancy. BMJ. 2007;334:1218-1220.
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