Understanding Skin Plaque

Different causes and kinds

Psoriasis on woman's knee
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A plaque is an elevated, solid, superficial lesion that is typically more than 1 centimeter in diameter and associated with a number of skin conditions, most commonly psoriasis. The word plaque is French for "plate."

What Causes Plaques?

The are several types of skin rashes and conditions associated with plaques, including eczema, psoriasis, pityriasis rosea, seborrheic dermatitis, tinea versicolor and ringworm.

The causes of some of these conditions, like ringworm, are known: fungi. Others, like psoriasis, are unknown. There are seven different types of psoriasis. Plaque psoriasis, known as psoriasis vulgaris, is the most common.

Although the exact cause of psoriasis is unknown, it's thought to be associated with the immune system and a type of white blood cell: T lymphocyte, or "T cell." T cells are constantly working to fend off viruses and bacteria, but for those with psoriasis, T cells are overactive and accidentally fight off healthy skin cells. In turn, there is an over production of healthy skin cells and more T cells and white blood cells, which disrupts the skin-shedding cycle.

New skin cells reach the outermost layer of the skin too quickly: in days, when it typically takes weeks. Because the dead skin and white blood cells can't shed fast enough, they build up and create thick, scaly plaques on the surface of the skin.

Appearance & Symptoms of Plaques

A plaque is a flat, primary lesion. Some plaques are flat; others appear as a thickened area of the skin that isn't visibly elevated above the surface of the skin. Plaques can have defined borders or not, and they can take on many different shapes, including:

  • Annular (ring-shaped)
  • Arcuate (half moon-shaped)
  • Polygonal (varied and not geometric)
  • Polymorphic (varied shapes)
  • Serpiginous (snake-shaped)
  • Poikilodermatous (variegated)

Plaques can appear anywhere on the body, but they appear most often on the elbows, knees, scalp and lower back. The amount of skin affected by plaques varies. Sometimes plaques are a few small spots that look similar to dandruff; other times they are huge eruptions that cover larger parts of the body, like the forearms.

The symptoms plaques are associated with vary depending upon the skin condition present. Generally, however, there are a few symptoms associated just with plaques:

  • Itching and burning
  • Soreness
  • Swelling and stiffness on joints where plaques are located

Diagnosis

Plaques are just one of the several types of primary lesions that indicate a skin disease. Doctors rely on the characteristics of the plaques in order to reach an accurate diagnosis. Typically a doctor will be able to make a diagnosis on the spot. A doctor will rarely take a skin biopsy, although it isn't unheard of.

 

Plaques can be a bit of a challenge to diagnose because they resemble several skin conditions, including seborrheic dermatitis, lichen planus, ringworm and pityriasis rosea. However, the plaques that appear due to these conditions possess different characteristics.

For example, seborrheic dermatitis plaques are scaly, itchy, red and typically found on oily parts of the body, including the face and chest. Pityriasis rosea plaques begin with one herald patch and spread. The plaques also resemble drooping tree branches. Doctors will make a diagnosis based upon the plaques' characteristics.

Treatment

Plaques, regardless of the skin disease they are associated with, are most often treated with a topical cream or ointment, like a corticosteroid or retinoid. Oral medication, like an antihistamine, may also be prescribed. Plaque psoriasis can be treated using light therapy.

Proper hygiene, regular use of a moisturizer, oatmeal baths and sun exposure (while wearing SPF, of course) are all said to ease discomfort and keep skin healthy, although they can't completely prevent plaques from occurring.

Sources:

http://www.mayoclinic.org/diseases-conditions/psoriasis/basics/definition/con-20030838

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