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lichen simplex chronicus

Saturday 17 June 2017

WKP PO

Definition :

Lichen simplex chronicus (LSC) is a skin disorder characterized by lichenification of the skin as a result of primary excessive scratching.

LSC (circumscribed neurodermatitis) is characterized by a central lichenificated plaque thickened and often hyperpigmented, usually surrounded by lichenoid papules and, along the borders with surrounding normal skin, by an indefinite zone of slight thickening.

The most common sites are the neck (sides), ankles, scalp, vulva, pubis, scrotum, and extensor forearms. The peak of incidence is between 35 and 50 years of age, and women are more affected than men (F:M = 2:1).

Microscopy

Lichen simplex chronicus has :
- marked hyperkeratosis
- focal parakeratosis
- prominent granular cell layer
- elongated rete ridges
- dermal perivascular infiltrate
- dermal interstitial infiltrate

- Early changes : spongiotic dermatitis

- Evolves to chronic changes

  • prominent acanthosis with curvilinear, blunt rete ridges
  • compact hyperkeratosis orthokeratosis with focal parakeratosis
  • hypergranulosis
  • papillary dermal fibrosis
  • variable intraepidermal infiltrate
  • variable superficial perivascular dermal infiltrate
  • Rare mast cells and eosinophils

The histopathological features in lichen simplex are epidermal hyperplasia, orthokeratosis, and hypergranulosis with a regular elongation of the rete ridges.

There is a perivascular infiltrate of lymphocytes and occasionally of macrophages. The macrophages are not clearly dendritic as in PN and much less numerous.

Moreover, in LSC there is no neural hyperplasia and abundancy of NGF and lack of positive immunostaining for NGF receptor mediators of pruritus as in PN.

Differential diagnosis

- psoriasis

- Other chronic spongiotic dermatitis / dermatitides

  • spongiosis
  • acanthosis
  • epidermal exocytosis
  • perivascular inflammatory infiltrate
    • predominantly lymphohistiocytic and occasional neutrophils and eosinophils (the latter may be numerous in allergic contact dermatitis)
    • Their differentiation may not be possible if superimposed lichenification is present

- prurigo nodularis (PN)

See also

- inflammatory cutaneous anomalies

  • nodular prurigo

Open references

- https://onlinelibrary.wiley.com/doi/full/10.1111/j.1529-8019.2008.00168.x