What are the types of parapsoriasis?

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

In 1902, Brocq initially described 3 major entities that fit the description:

  • Pityriasis lichenoides (acuta and chronica)

  • Small plaque parapsoriasis

  • Large plaque parapsoriasis (parapsoriasis en plaque)

Pityriasis lichenoides (acuta and chronica)

Pityriasis lichenoides variants describe scaly dermatoses with necrotic papules that are clinically and histologically different from parapsoriasis. These diseases generally are benign and undergo spontaneous resolution but, at times, may have a protracted course (see Pityriasis Lichenoides for further discussion).

Large plaque and small plaque parapsoriasis

Current terminology of parapsoriasis refers to 2 disease processes that are caused by T-cell–predominant infiltrates in the skin. These disease processes are large plaque parapsoriasis and small plaque parapsoriasis.

As the nomenclature and description of the disease spectrum under the descriptive term parapsoriasis evolved, the primary focus has been on the distinction of whether the disorder progresses to mycosis fungoides (MF) or cutaneous T-cell lymphoma (CTCL). Small plaque parapsoriasis is a benign disorder that rarely if ever progresses. Large plaque parapsoriasis is more ominous in that many patients progress to MF/CTCL. [1] Other cases have given rise to lymphomatoid papulosis. [2]

Controversy exists currently in the classification of large plaque parapsoriasis because some believe it is equivalent to the earliest stage of CTCL, the patch stage. [3, 4, 5] A meta-analysis from 2016 supports a risk of transformation to early CTCL, and newer technology may allow for earlier diagnosis. [6, 7]

The duration of parapsoriasis can be variable. Small plaque disease lasts several months to years and can spontaneously resolve. Large plaque disease is chronic, and treatment is recommended because it may prevent progression to CTCL.

El-Darouti et al reported on a 7-year study of a hypopigmented disorder that the researchers believe should be classified as a new variant of parapsoriasis en plaque. [8]

No clear etiology for small plaque or large plaque parapsoriasis is known, and no specific association has been made with contact exposure or infections.

For more information, see the topic Psoriasis.


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