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General Information

Parapsoriasis is a group of diseases that can be subdivided in two general forms: Small Plaque and Large Plaque. Small plaque parapsoriasis is a benign disorder that rarely progresses. The plaques appear on patients as small circular lesions with some slight scaling in a light pinkish coloring. Small plaque lesions measure less than 5 cm in diameter. Large plaque parapsoriasis manifests as faint erythematous patches with arcuate geographic borders. Large plaque parapsoriasis often evolved into CTCL and appears on patients as flaky thin scales with a wrinkling appearance. The plaques are larger then 6 cm in diameter, and possess a faint red to pink coloring. Small plaque parapsoriasis is usually asymptomatic, treatment is prescribed to alleviate the dry lesions on the skin. The treatment for small plaque parapsoriasis include mid potency topical steroids, emollients or phototherapy. Large plaque parapsoriasis treatments include mid to high potency topical steroids, topical nitrogen mustard, topical carmustine or phototherapy. Large plaque parapsoriasis should be followed up at 6 months interval to assure that progression to Mycosis Fungoides or Cutaneous T-cell lymphoma has not occurred.

No accurate statistics on the incidence and frequency


Develops from a few patches, which become more visible over time

Small plaque – well-circumscribed, slightly scaly, light salmon-colored patches, measuring >5 cm in diameter, scattered over trunk and extremities. Large plaque – faint erythematous patches with arcuate geographic borders, measuring <6 cm in diameter, scattered over proximal extremities and trunk. Histology
Small Plaque – Superficial perivascular lymphocytic infiltrate with a nonspecific inflammatory infiltrate of CD4+ and CD8+ T cells. Large plaque – a superficial dermal inflammatory infiltrate consists predominantly of lymphocytes

1. “Parapsoriasis” (Online). November 2005. http://www.merck.com/mmpe/sec10/ch116/ch116c.html (visited: April 1, 2008) 2. “Parapsoriasis” (Online). February 2007. http://www.emedicine.com/DERM/topic311.htm (visited: April 1, 2008

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