Clinical Features:

• Poorly defined entity with overlap with mycosis fungoides
• Two clinical forms exist:
  • Small-plaque parapsoriasis (digitate dermatosis, chronic superficial dermatitis) presents as ovoid or digitate plaques measuring 2 to 6 cm in diameter, with a predilection for the lateral trunk.  The plaques have a reddish or yellowish surface with wrinkling and mild scaling.  The prognosis is excellent.
  • Large-plaque parapsoriasis (psoriasis en grandes plaques, see separate textbook entry) presents as a small number of well-defined, reddish, scaly plaques typically measuring over 10 cm in diameter on the trunk or extremities.

Histologic Features:

• The features are very nonspecific, and distinction from early mycosis fungoides and eczema may be difficult.
• Mild upper dermal perivascular lymphocytic infiltrate
• Mild epidermotropism of lymphocytes, without Pautrier microabscesses, is sometimes present.
• Mild acanthosis
• Patchy parakeratosis
• The lymphocytes have a helper T-cell immunophenotype: CD3+, CD4+, CD8- with a few admixed CD8+ cells.

Cases associated with this book:

Parapsoriasis
Author: Stephen Lyle, M.D., Ph.D.

Conference: DermatopathologyConsultations.com Teaching Collection