What is the pathophysiology of large plaque parapsoriasis (LPP)?

Updated: Sep 04, 2019
  • Author: Henry K Wong, MD, PhD; Chief Editor: Dirk M Elston, MD  more...
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Answer

Large plaque parapsoriasis is a chronic inflammatory disorder, and the pathophysiology has been speculated to be long-term antigen stimulation. This disorder is associated with a dominant T-cell clone, one that may represent up to 50% of the T-cell infiltrate. If the histologic appearance is benign, without atypical lymphocytes, classification of large plaque parapsoriasis is made. If atypical lymphocytes are present, many would classify such patients as having patch stage CTCL.

In one study, human herpesvirus type 8 was detected in up to 87% of skin lesions of large plaque parapsoriasis. This is the first association of a specific infectious agent with large plaque parapsoriasis, and the significance is unclear. Further studies are important to determine the significance of this finding. [11]

The close relationship between large plaque parapsoriasis and mycosis fungoides is highlighted by the detection of TOX expression, a new marker that has been described to be frequently detected in the abnormal T cells in mycosis fungoides. In one study, large plaque parapsoriasis has expression of TOX similar to that of mycosis fungoides. [12]


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