The cause of lichen planus is unknown. However, there are distinct trigggering factors for this condition. These include medications (antihypertensives, antimalarials, antiepileptics and anti-TB drugs). An underlying infection has also been postulated as a trigger for the development of lichen planus.
The characteristic features of lichen planus is the violaceous colour and the presence of itching (pruritus).The skin lesions are polygonal, raised and tend to have a shiny surface. The characteristic sites of involvement on the skin includes the flexures of the wrists, armpits, trunk and lower back region. The lesions may appear thickened and involve the lower limbs.
Scalp- Here lichen planus presents with pigmented patches centred around the hair follicle. If untreated, it may lead to scarring and hair loss (alopecia).
Oral mucosa – the lesions may appear in net pattern with fine lacy lines affecting the buccal mucosa. Alternatively, they may appear as painful erosions and ulcers affecting the oral mucosa. If left untreated, there is a small chance of malignancy.
Nails- the nails may appear gritty with a sandpaper texture appearing on the surface. The skin may also be drawn inwards to the nail plate. This is referred to as a pterygium.
Genitalia- this condition may present as small patches affecting the genitalia.
The treatment of lichen planus is symptomatic. The treatment options include:
· Topical corticosteroids
· Intralesional steroids for hypertrophic lesions
· Oral steroids
· Oral antihistamines
· Systemic antibiotics- Metronidazole
· Oral retinoids- eg. Acitretin (Neotigason)
· Ultraviolet therapy- UVB/PUVA therapy
· Immunosuppressive treatment- MTX/Cyclosporine/Cellcept
Excimer laser-for resistant localised lesions.