Clinical Features:

• "Five Ps": polygonal, planar (flat-topped), pruruitic, purplish papules and plaques, most commonly on flexor surfaces of the extremitites. 
• Some cases are associated with hepatitis C.
• White lines called "Wickham's striae" are sometimes present.

Histologic Features:

• Compact hyperkeratosis
• Hypergranulosis (may be wedge-shaped)
• Irregular acanthosis with "saw tooth" rete ridges
• Colloid bodies (stain with IgM on immunofluorescence)
• Vacuolar change of the basal layer
• Lichenoid lymphocytic infiltrate
• Melanin incontinence is often present
• The presence of parakeratosis argues against the diagnosis of lichen planus.
  

Cases associated with this book:

Lichen planus
Author: Stephen Lyle, M.D., Ph.D.

Conference: DermatopathologyConsultations.com Teaching Collection