Lichen planus

This is a condition of unknown aetiology characterized by intensely pruritic shiny, flat topped, violaceous, polygonal papules that are usually seen on the flexural surfaces of the wrists, arms and legs (1). Other affected sites include:

• trunk and thighs (1)
• mucous membranes are often affected e.g. - buccal mucosa, female genitalia
• penis - mostly annular lesions
• scalp - will lead to scarring if untreated.
• nails (2)

It commonly affects people between the ages of 30 and 60 years and can be seen in both sexes (1). Lichen planus lesions may evolve gradually over several weeks or may develop rapidly (2). It may present as:

• Grouped
• Annular
• Generalized lesions (1)

This is a condition of unknown aetiology characterized by intensely pruritic flat topped papules that are usually seen on the inner aspect of the elbows and wrists. The mucous membranes are often affected.

The condition can cause painful erosive lesions in the oral cavity, increasing the risk of secondary infections and possibly malignant transformation into oral squamous cell carcinoma, although there is no proven association. (3)

Click here for example images of lichen planus

Notes:

• HLA halotypes (e.g. HLA-DR1 in cutaneous LP) and rare cases of familial LP suggest that genetic factors may have a role in susceptibility
• autoimmune disorders like ulcerative colitis and alopecia areata occur more frequently in LP patients than controls
• is a significant association between Hepatitis C (HCV) infection and LP, although there is no known explanation for this (4)
• many drugs (e.g. gold, penicillamine, antimalarials) and amalgam fillings can cause lichenoid reactions (5)

Reference:

1. Solimani F, Forchhammer S, Schloegl A, Ghoreschi K, Meier K. Lichen planus - a clinical guide. J Dtsch Dermatol Ges. 2021 Jun;19(6):864-882.
2. Primary Care Dermatology Society (UK). Lichen planus
3. Gonzalez-Moles MA, Scully C, Gil-Montoya JA. Oral lichen planus: controversies surrounding malignant transformation. Oral Dis. 2008 Apr;14(3):229-43.
4. Lodi G, Giuliani M, Majorana A, et al. Lichen planus and hepatitis C virus: a multicentre study of patients with oral lesions and a systematic review. Br J Dermatol. 2004 Dec;151(6):1172-81.
5. Maul JT, Guillet C, Oschmann A, et al. Cutaneous lichenoid drug eruptions: a narrative review evaluating demographics, clinical features and culprit medications. J Eur Acad Dermatol Venereol. 2023 May;37(5):965-75.