Skin inflammatory (nontumor)
Spongiotic, psoriasiform and pustular reaction patterns
Pityriasis rubra pilaris

Author: Mowafak Hamodat, M.D., MB.CH.B, MSc.

Revised: 15 October 2018, last major update August 2011

Copyright: (c) 2002-2018,, Inc.

PubMed Search: Pityriasis rubra pilaris [title] skin

Cite this page: Hamodat, M. Pityriasis rubra pilaris. website. Accessed December 16th, 2018.
Definition / general
  • Rare, chronic, papulosquamous dermatosis of unclear etiology
  • Salmon-colored scaly patches, affecting elbows/knees or entire body, usually adults > age 40 years
Clinical features
  • Salmon-colored scaly patches surrounding normal skin
  • Divided into five types: classic adult, atypical adult, classic juvenile, circumscribed or atypical juvenile
Case reports
  • Accutane
Clinical images

Images hosted on other servers:

Entire body affected except trunk

Various images

Microscopic (histologic) description
  • Biopsy from non-follicular lesion consists of alternating orthokeratosis and parakeratosis in both vertical and horizontal directions
  • Focal or confluent hypergranulosis, thick suprapapillary plate, broad epidermal ridges, narrow dermal papillae and perivascular lymphocytic infiltrate in the superficial dermis
  • Small numbers of plasma cells and eosinophils may be present
  • Superficial blood vessels may appear slightly dilated
  • Occasionally, mild spongiosis with scattered intraepidermal lymphocytes
  • In early lesions, parakeratosis is poorly developed and lamellar ortho hyperkeratosis predominates; hypergranulosis is present and rete ridges are broadened and slightly elongated; the suprapapillary plate may be mildly thickened
Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Hillary Rose Elwood, M.D.

PRP patient with alternating ortho and parakeratosis, focal follicular plugging

Differential diagnosis
  • Psoriasis: acanthosis is more marked, and often strikingly regular, rete are thin and often fused, supapapillary plate is thinned, parakeratosis is usually confluent and characteristic collections of neutrophils are seen in overlying parakeratotic stratum corneum associated with spongiform degeneration of the underlying superficial epidermis
Additional references