Plamar lichen planus can be difficult to diagnose if present as an isolated finding. Itchy (or painful) erythematous scaly plaque is characteristic. The lesions tend to be firm and rough with a yellowish hue. It is one of the therapy-resistant variants of lichen planus. Although lesions on the volar aspect of the wrists are common, lesions on the adjacent palms are less common and lack the characteristic shape and colour of lesions elsewhere. They may be broadly sheeted or show up as punctate keratoses. Vesicle-like papules are recorded. Itching may be absent. Palmoplantar lichen planus may also present as erosive-ulcerative type. When such changes occur in isolation, diagnosis is difficult; and conditions such as eczema, tinea, secondary syphilis, psoriasis, porokeratosis, callosities and warts must be excluded. Histopathologically findings are identical to those of classic lichen planus.
The primary lesions of lichen planus are characteristic, almost pathognomonic violaceous, flat-topped, polygonal papules. Papules expand to plaques. The colour of the lesions initially is erythematous but well-developed lesions are violaceous, and resolving lesions are often hyperpigmented. The surface is shiny with scant adherent scales. On the surface, grey or white lines, known as Wickham’s striae, may traverse the surface of the papules. Dermoscopy may enhance the visualization of this important diagnostic element. Most patients react to the itching of lichen planus by rubbing rather than scratching but itching can be absent. The four Ps-purple, polygonal, pruritic papule are a mnemonic to help you recall the findings that characterise lichen planus. The centre of the papule shows irregular acanthosis of the epidermis, irregular thickening of the granular layer, and compact hyperkeratosis. A focal increase in thickness of the granular layer and infiltrate corresponds to the presence of Wickham’s striae. The basal damage is associated with a band-like infiltrate of lymphocytes and some macrophages which press against the undersurface of the epidermis. Occasional lymphocytes extend into the basal layer. The infiltrate however does not obscure the interface or extend into the mid-epidermis. Pigmentary incontinence with dermal melanophages is characteristic. Postinflammatory pigmentation may persist for some time.
Potent topical corticosteroids (with or without occlusion) remain the treatment of choice for lichen planus in patients with classic and localized disease.
|Improvement after use of very potent topical corticosteroid with occlusion|
This page was last updated in August 2014.