Lichen is defined as certain plants formed by the mutualistic combination of an alga and a fungus. There are a group of papular skin conditions called lichen planus, lichen sclerosus, lichen simplex chronicus and lichen amyloidosis which will be discussed in details below.
What is Lichen Planus?
Lichen planus is an itchy, papulosquamous skin disorder often associated with hepatitis C infection. It can affect the skin, oral mucosa, nails, scalp and genitalia area. It can occur at any age and any race. Males and females are equally affected.
What causes Lichen Planus?
Lichen planus is caused by a cell-mediated immune response of unknown origin. It is highly associated with people with hepatitis C infection. It is also found in patients with other autoimmune diseases such as Vitiligo, ulcerative colitis, alopecia areata, myasthenia gravis and dermatomyositis.
Lichen planus may have some genetic predisposition. Affected families may have HLA-B7 (human leukocyte antigen B17), HLA-DR1 (Human Leukocyte antigen DR1) and HLA-DR10 (human leukocyte antigen D10.
Clinical presentation of Lichen Planus
Lichen planus clinical features are best described by the 6 Ps: Purplish, Pruritic (itchy), Planar, Polygonal shaped, Papules (small solid bumps) and Plaques (solid raised flat topped lesion). The rash also has characteristic white lines across it called Wickham Stria. The rash typically affects the wrists, lower back and ankle areas. Koebner phenomenon i.e. rash appears after scratching of the skin is characteristic of lichen planus.
Oral mucous lichen planus commonly affect the tongue and buccal mucosal area. The lesions are white or gray streaks which form reticular or linear pattern on a purplish background. Ulcerative lesions in men who smoke have an increased risk of cancerous change.
Lichen planus can involve the genitalia area. In men it can be found on the glans penis. In women, the vulvar area is involved. It can cause itch, painful intercourse, burning sensation and also urethra stenosis.
Nail involvement is found in 10% of cases. The nails will have longitudinal ridging, grooving, hyper-pigmentation, hyperkeratosis (abnormal thickening) and onycholysis (separation of nail from nail bed).
There are many variants of lichen planus depending on the site involved.
Diagnostic tests of Lichen Planus
1.Skin biopsy for histopathological analysis is diagnostic of lichen planus.
2.Direct Immunofluorescence study will show deposits of Immunoglobulin M and complement mixed with keratinocytes.
3.Blood tests like hepatitis B and C and liver function test may be necessary due to its association with lichen planus.
Treatment of Lichen Planus
Most lichen planus is self-limiting disease which may resolve in 8 to 12 months. For mild cases, topical steroids may be just enough. For moderate to severe cases or cases that involve the scalp, oral cavity and nails may require more extensive systemic treatment.
First line treatment involves application of topical potent steroids like clobetasol/ betamethasone valerate 0.1% twice daily. If it doesn’t work intra-lesional steroids like triamcinolone can be given. For extensive severe cases or cases with dystrophic nails or scarring alopecia, then oral steroids may be used with a tapering dose.
Second line treatment includes topical calcipotriol (tacrolimus/pimecrolimus creams), oral retinoids, phototherapy with PUVA/ narrow band UVB.
Other treatment includes oral antibiotics like metronidazole and also immunosuppressant like cyclosporine.
What is Lichen Sclerosus?
Lichen Sclerosus is a long-standing inflammatory skin disorder which commonly affects the genitalia and peri-anal areas. A small proportion of Lichen Sclerosus cases involve non-genitalia sites. This condition was previously known as lichen sclerosus et atrophicus. It results in white plaques with resultant permanent scarring and epidermal atrophy. It results in an increased risk of squamous cell carcinoma (skin cancer) in the genitalia area.
It occurs more commonly in females than males. In males involved, lichen sclerosus more commonly occur in males who are uncircumcised. It can occur at any age even in pre-puberty children. For adult women it occurs more frequently after age 50.
What causes Lichen Sclerosus?
The exact etiology is unknown. It may be caused by hormonal, genetic, infectious and environmental factors. The presence of antibodies to glycoprotein extracellular matrix protein 1 (ECM1) seem to suggest it is caused by autoimmune process. These antibodies cause vasculature changes. It may be associated with other autoimmune conditions likealopecia areata, psoriasis, Vitiligo and morphoea.
There are also evidence of ongoing inflammation and changes in fibroblast function which leads to fibrosis and scarring of the upper dermis.
Clinical Presentation of Lichen Sclerosus
Lichen Sclerosus will usually begin as white polygonal which will then conform into plaques. The affected skin will turn porcelain white in appearance.
Vulvar Lichen Sclerosus: Lichen Sclerosus which involves the vaginal area will result in itch, pain during intercourse (dyspareunia), painful urination (dysuria) and genitalia bleeding. The skin of vulva may have white thickening. Occasionally the clitoris may shrink, the labia minora may be obliterated and the entrance to vagina tightens. Bruises, blisters and ulcer may also be present over at the vulva areas. It may increase the risk of vulvar cancer.
Penile Lichen Sclerosus: Lichen Sclerosus which involves the penile are will results in itch, urinary obstruction (due to constriction of urethra) and also phimosis (abnormal constriction of foreskin that prevents it from retracting). The tip of the penis is more commonly involved may become firm and white.
Non-genitalia Lichen Sclerosus: it can occur at any part of the body, more commonly over the shoulders and back. White patches with wrinkled surface will be seen on the skin involved.
Diagnosis of Lichen Sclerosus
Skin Biopsy is confirmatory test for diagnosis. The biopsy sample is sent for histopathology studies. Typical histopathological findings of lichen planus include lichenoid infiltrates in the dermal-epidermal junction,remarkable edema in the papillary (upper) upper dermis is replaced by a dense, homogenous fibrosis as the lesion matures and there will be compact hyperkeratosis with stratum corneum.
Treatment of Lichen Sclerosus
Non-genitalia lichen sclerosus with no symptoms usually do not require treatment.
Genitalia lichen sclerosus can be treated with topical strong steroids, calcineurin inhibitors (tacrolimus, pimecrolimus) and topical retinoids. Systemic oral steroids and retinoids in more severe cases may be beneficial too.
Surgery like circumcision may benefit males with lichen sclerosus and those with phimosis. Vulval surgery may be necessary for those with vulval cancer. There are also surgeries for vulvar adhesions to reduce urination and reduce pain during intercourse.
What causes Lichen Simplex Chronicus?
The exact underlying etiology is unknown. Usually itch provokes scratching and rubbing which leads to skin thickening and worsening of rash. Conditions like atopic dermatitis and Stasis Dermatitis may predispose patients to lichenification with chronic scratching.
Clinical presentation of Lichen Simplex Chronicus
It tends to be found on skin accessible to scratching. There will be red scaly thickened well-demarcated skin plaques on places like scalp, nape of neck, extensor of forearms/elbows, lower limbs and genitalia areas. Post inflammation hyper-pigmentation may occur.
Diagnostic Tests for Lichen Simplex Chronicus
1.Blood serum immunoglobulin E may support the diagnosis of Atopic Diathesis.
2.Skin scrapings and culture to rule out fungal infection.
3.Skin Patch Test to exclude allergic contact dermatitis.
4.Skin biopsy to exclude other skin disorders.
Treatment of Lichen Simplex Chronicus
Treatment involves stopping the itch and abstains from scratching. Oral antihistamines can be given to reduce itch. Topical moisturizer is encouraged to maintain the integrity of the skin barrier.
Topical moderate to strong steroids are useful in softening the thickened skin and to reduce the inflammation. Topical antibiotics can be used on infected areas. For those who do not respond to topical steroids then topical immunomodulators like tacrolimus/pimecrolimus may be used
What is Lichen Amyloidosis?
Lichen amyloidosis is a skin condition whereby the protein amyloid is deposited on the skin. It is more common in males and affects in persons age 50-60s. This condition is also more common in Chinese.
It may be associated with syndromes like MEN 2A (multiple endocrine neoplasia type 2A syndrome) and Sipple syndrome.
What causes Lichen Amyloidosis?
The amyloid proteins bind to the anti-keratin antibodies and result in altered keratins as a source for the skin deposits.
Clinical presentation of Lichen Amyloidosis
Patient always present with an intense itchy reddish brown thickened papules on the skin. It commonly occurs over the shin areas. It can also occur at the thighs and feet areas.
Diagnostic tests for Lichen Amyloidosis
1.Skin biopsy can be done for confirmation.
Treatment for Lichen Amyloidosis
Lichen amyloidosis is extremely itchy in nature so oral antihistamines can be given to reduce the itch. Topical and also intra-lesional steroids can be used. There may also be improvement if topical immunomodulators like tacrolimus is used.
Other treatments with topical dimethyl sulfoxide (DMSO), etretinate and pulsed dye laser have shown to improve the conditions of some patients. The skin lesions do recur after surgical intervention so usually surgical removal is not highly recommended.