Pityriasis rubra pilaris pathology

Author: Assoc Prof Patrick Emanuel, Dermatopathologist, Auckland, New Zealand, 2014.


Pityriasis rubra pilaris or PRP presents clinically as a papulosquamous eruption with follicular plugging and perifollicular erythema. The various clinical forms share the same histopathologic features.

Histology of pityriasis rubra pilaris

In PRP, the epidermis shows regular acanthosis and psoriasiform hyperplasia (figures 1-3). The horn is thickened with parakeratotic foci between orthokeratosis both vertically and horizontally (not seen clearly in the presented images). The hyperkeratosis tracks down the openings of follicular structures forming follicular plugs (figures 1-3). The dermis may contain a mixed sparse infiltrate which may be lichenoid. Rarely, foci of acantholysis may be seen (figure 3) and some authors have made associations with Darier disease.

Pityriasis rubra pilaris pathology

Special studies for pityriasis rubra pilaris

None are generally needed. PAS may be helpful to rule out fungal infections.

Differential diagnosis of pityriasis rubra pilaris

Psoriasis – Neutrophilic infiltrates and spongiform pustulation are clues to psoriasis.

Syphilis – Can be in the differential with there is a psoriasiform eruptions with lichenoid features and plasma cells.

Mycosis fungoides – Mixed psoriasiform spongiotic and lichenoid patterns raise the possibility of mycosis fungoides or parapsoriasis.

Ask an online dermatologist now
Securely upload your symptoms and pictures using First Derm
(Sponsored content)

 

Related information

 

References:

  • Weedon's Skin Pathology (Third edition, 2010). David Weedon
  • Ko CJ, Milstone LM, Choi J, McNiff JM. Pityriasis rubra pilaris: the clinical context of acantholysis and other histologic features. Int J Dermatol. 2011 Dec;50(12):1480-5.

On DermNet NZ:

Books about skin diseases:

See the DermNet NZ bookstore