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Psoriasis is an immune-mediated skin disease that most commonly presents as a red, scaly plaques caused by excessive proliferation of skin cells.

Psoriasis is five times less common in Asian than in people of Caucasian descent. The most common incidence is within the 15-30 year (Type I) age group, after which the incident falls, but there is a revival of incidence in the 50-60 year (Type II) age group.

Psoriasis has been recognized in China as a disease condition for at least 2000 years and has had the following names: Gan Xuan (干癣) which means “dry lichen”; She Shi (蛇虱) which means “snake lice”; and Bai Bi (白疕) which means “white crust”; Song Pi Xuan (松皮癣) which means “pine skin lichen”.

Psoriasis does come in different presentations, including:

Plaque Psoriasis

This is the most common form and is easiest to recognize. Plaque psoriasis presents as well-defined, symmetrical red plaques, with the most common locations being:

  • Ear: within and around the ears
  • On the scalp and bordering the hairline
  • Extensor aspect of elbows and knees
  • Torso: especially the lower back

Inverse/flexural psoriasis (less common) is when lesions appear in ‘folded’ areas (flexures). These include:

  • Armpits
  • Under the breasts
  • Umbilicus (navel)
  • Groin & private parts
  • Natal cleft (butt crack) or perianal

There are often other signs, often as the condition aggravates or becomes longstanding. These include:

  • Auspitz: bleeding when deepest scales is removed
  • Kobner: isomorphism, meaning that trauma around a lesion elicit new, similar-looking lesions
  • Nails: pitting onycholysis, “oil spots”

Guttate Psoriasis

This is commonly seen in children, usually lagging between 2-6 weeks behind an upper respiratory tract infection. It presents as small bumps (papules) that spread out usually on the torso area. While this can be self-limiting and resolve within a few months, it may also hearld the onset of plaque psoriasis.

Pustular Psoriasis

There is palmoplantar psoriasis, which can be seen as a variant of palmoplantar pustulosis — this presents as pustular lesions in the palms and soles, with the lesions often showing up as yellowish pustules which then burst and form brownish crusts with scales. The palms and soles usually appear as slightly swollen and red.

There is also Von Zumbusch pustular psoriasis, a more severe presentation with fever and breakouts over large areas of your body.

Erythrodermic psoriasis

This is a serious progression affecting a small number of people suffering from psoriasis. The whole body is almost fully red, with scaling and erythroderma. Because it is a systemic affliction, there will be fever and an intense feeling of heat.

Erythroderma is a secondary presentation which may follow from different primary skin conditions, including atopic dermatitis, contact dermatitis or drug eruption (allergy to certain medications). This is also how some people coming in for ‘Topical Steroid Withdrawal’ aka ‘Red Sleeve Syndrome’ present as.

Psoriatic Arthritis

This is when the person suffers from both pain in the joints and psoriasis. The athritis is often seronegative, and has the following manifestations:
a. Mono or asymmetric oligoarthritis
b. Arthritis of the distal interphalangeal joints (DIPs)
c. Rheumatoid arthritis-type presentation
d. Arthritis mutilans
e. Spondylitis/sacroilitis