Lichen planus is an inflammatory disorder of the skin and mucous membrane. Lesions are dense, a band like (lichenoid) infiltrate in the upper dermis. Young adults are commonly affected but it can occur at any age. Both males and females are affected equally.
The cause of Lichen planus is unknown but it is believed to be an autoimmune disease caused by T cell mediated autoimmune destruction of epithelial cells.
Various causal or triggering agents are identified which are termed as Lichenoid reaction. These may include:
- Drug reaction (Gold salts, beta blockers, antimalarials like quinine, thiazide diuretics, furosemide, spironolactone, metformin, and penicillamine),
- Reactions to amalgam (metal alloys),
- Graft vs host disease lesions,
- Hepatitis (hepatitis B, hepatitis C, and primary biliary cirrhosis),
- Mercury exposure.
Based on morphology and configuration:
- Annular: ring like,
- Vesicular and Bullous,
- Hypertrophic:large thick plaques on shin, ankle or foot,
- Atrophic: Macular flat lesions,
- Follicular: Conical papules with central keratin plug.
Based on distribution:
- Acute widespread,
- Chronic widespread,
Signs and Symptoms
Flat-topped, polygonal, violaceous, erythematous, 2-10 mm papules covered with scanty scales are characteristic Application of oil to the surface of the papules shows fine crisscross white lines termed as Wickham’s striae. initial lesions are tiny 1-2 mm but the later coalescence of lesions may lead to the formation of larger 2-5 mm plaques.The occurrence of lesions within scratch marks (known as Koebner phenomenon) is an indication of activity of the disease.
The description is known as the characteristic “6 P’s” of Lichen planus: Planar (flat-topped), Purple, Polygonal, Pruritic, papules, and Plaques.
Distribution is usually on flexor aspects of wrists and forearms, shin, ankles, dorsum of feet, anterior thighs and flanks are sites of predilection. Oral especially buccal mucosa, lips, and genitalia are also commonly affected. Mucosal lichen planus includes esophageal and genital variants.
Diagnosis is primarily done clinically by characteristic “lichen like” appearance. For doubtful cases to rule out conditions resembling lichen planus, a biopsy may be done.
There is no cure for lichen planus, so treatment is only symptomatic or for cosmetic reasons. Without treatment, most lesions will spontaneously resolve within 6-9 months for cutaneous lesions.
Avoidance of any precipitating factors should be done. For itching, oral antihistaminics like levocetirizine and desloratadine can be given. Potent corticosteroids are effective for ordinary lesions. Stronger steroids may be used for hypertrophic lesions. in such cases, patient needs to be monitored for side effects of potent topical steroids.
For widespread lichen planus, systemic corticosteroids may be considered.
Cosmetic treatments include laser surgery, cryotherapy, and phototherapy.
For Oral lesions, elimination of precipitating factors and improving oral hygiene are initial management. treatment involves topical corticosteroids and analgesics. In severe condition systemic corticosteroids may be used. Sometimes calcineurin inhibitors and retinoids may be used.
Oral lesions are difficult to treat with relapses being common.Atrophic/erosive lichen planus is associated with small risk of malignant transformation.