Lichen planus is a chronic pruritic self limiting inflammatory dermatosis that is commonly associated with mucosal involvement and rarely with nail dystrophy and scaring alopecia.
It usually involves flexor aspext of wrist adn lower legs. In mucosal involvement mouth, anogenital region, oesophagus.
Risk factors:
- most imp: dental amalgum (due to mercury)
- infection: hepatitis b & c
- drugs like antimalaria, ACEIs, B-blockers
Etiopathogenesis:
It is T-cell driven immune mechanism.
A mixed lymphohistiocytic infiltrate is seen at dermoepidermoid junction, which becomes ragged and saw-toothed. Basal layer shows liquefactive degeneration. Acanthosis and Hyperkeratosis of the epidermis.
Clinical Features:
- tiny
- pappule
- pruritic
- purple
- plane-topped
- polygonal
- Wickham's striae: whitish linear streaks seen on surface under oil immersion field.
- Koebner's phenomenon: aka isomorphic response, indicate active form, similar morphological lesion seen along lines of trauma
- Scaring alopecia in scalps
- Nails may be dystrophic
- Hyperpigmentation after resolution
Variants:
- Atrophic
- Hypertrophic
- Annular
Investigation:
usually not done, but histopathology can be done which shows:
- Hyperkeratosis: rover Stratum corneum
- Wedge shaped hypergranulosis in St. granulosum
- Saw-toothed rete ridge
- Acanthosis: Thickening of the stratum spinosum
- lyphocytic infiltrates in dermoepidermal junction
- necrotic keratinocytes
- basal cell degeneration
- artefactual cleft at DEJ
Treatment:
General measures:
- counseling, reassurance and emotional support
- physical activity and metal rest is adjuvant
Specific measures:
- Topical : Clobetasol, intralesional steriods
- Systemic: oral prednisolone, methotrexate, dapsone
- Others: PUVA, retionoids, azathioprine