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pityriasis rubra pilaris

Wednesday 1 June 2016


Definition : Rare, chronic, papulosquamous dermatosis of unclear etiology.


- Pityriasis rubra pilaris. Prominent follicular plugging w/ psorisasiform hyperplasia


- prominent follicular plugging or focal follicular plugging
- psorisasiform hyperplasia
- alternating orthokeratosis and parakeratosis in both vertical and horizontal directions
- focal or confluent hypergranulosis
- thick suprapapillary plate
- broad epidermal ridges
- narrow dermal papillae
- perivascular lymphocytic infiltrate in the superficial dermis
- small numbers of plasma cells and eosinophils may be present
- superficial blood vessels may appear slightly dilated
- +/- 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

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
  • characteristic collections of neutrophils are seen in overlying parakeratotic stratum corneum associated with spongiform degeneration of the underlying superficial epidermis

See also

-  cutaneous anomalies