Lichen planus can be easily identified in most cases on account of the typical location of the spots and their characteristic 'violaceous' appearance.

The skin eruptions of lichen planus tend to involve:

Insides of the wrists

Ankles

Lower back

Scalp

Nails

Mucous membranes that line the mouth, nose, genitals (vagina / penis) and anus

The onset of the eruptions can be sudden or gradual and it shows the following features:

Rows or small clusters of flat-topped eruptions usually few millimeters in diameter

Violaceous color of rashes in most cases; the color may vary from purple to pink to red

Itching which may vary from mild to severe

New eruptions may appear at sites of minor skin injury such as a superficial scratch (called as Koebner's phenomenon)

In some cases, there may be thick, reddish-brown lesions that are covered with scales (called as hypertrophic lichen planus)

When the rashes resolve, they leave behind dark brown or gray spots (hyperpigmentation marks)

In cases of scalp involvement there can be development of scarring in affected areas leading to loss of hair (alopecia areata)

Nail affection may give rise to pits and grooves in the nails

Oral lichen planus has a typical presentation that involves:

Small, pale, raised areas that form a lacy network on the inside of the cheeks, rarely involving the tongue; occasionally the lesions may be red and shiny

Soreness, burning pain, tenderness - especially while taking spicy foods

Dry mouth with metallic taste or blunted taste sensation

Painful, recurrent ulcers in the mouth characterize one of the forms called erosive lichen planus

People with long-term lesions of lichen planus are at greater risk of developing malignancy (squamous cell carcinoma).