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pityriasis rubra pilaris
Wednesday 1 June 2016
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Definition : Rare, chronic, papulosquamous dermatosis of unclear etiology.
Images
Pityriasis rubra pilaris. Prominent follicular plugging w/ psorisasiform hyperplasia
Synopsis
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
- 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
