Dermatology · Pathway 16

Lichen Planus & Pityriasis Rosea

Standard dermatology Linear

Key points

Lichen planus: 6 P's — Pruritic · Purple · Polygonal · Planar (flat-topped) · Papules · Plaques; Wickham's striae (lacy white surface); Koebner phenomenon.
Oral lichen planus: lacy white buccal pattern; small malignant potential.
Associations: hepatitis C, drugs (beta-blockers, ACE inhibitors, thiazides, antimalarials, gold).
Pityriasis rosea: herald patch → secondary eruption of oval scaly plaques in 'Christmas tree' distribution on trunk; self-limiting ~6 weeks.
Pityriasis versicolor (Malassezia): hypo/hyperpigmented scaly patches on trunk.