Lichen Planus Flashcards

Lichen Planus

Introduction

Lichen planus is a mucocutaneous disorder. The word lichen planus comes from the Greek words. $lichen$ means tree moss and $planus$ means flat. Erasmus Wilson, a dermatologist, first reported the condition in 1869. Oral lesions were first described by Theirbergie. Wickham in 1895 described the appearance of whitish striae that develop atop the flat-surfaced papules.

Definition

Oral lichen planus (OLP) is a common chronic immunological inflammatory mucocutaneous disorder. Its appearance varies from keratotic (reticular or plaque-like) to erythematous and ulcerative.

Etiopathogenesis

The exact etiology is still unknown, but OLP is considered a T cell-mediated disorder. Cytokines are produced, leading to apoptosis. Cytotoxic $CD8+T$ lymphocytes are responsible for apoptosis of keratinocytes in the basal cell layer. Autologous antigen peptides from basal cells are presented by Langerhans cells to autoreactive T cells, inducing apoptosis in the basal cell layer and leading to clinical lesions.

Other possible theories include:

• Genetic background (weak association between HLA antigen and lichen planus)

• Dental materials

• Infectious agents (Gram-negative aerobic bacillus, spirochetes, and Candida species)

• Psychological factors (anxiety, depression, psychic disorders in erosive lichen planus)

Clinical Features

• Commonly affects adults.

• Female predilection with a ratio of 2:1.

• White papules coalesce, forming a network of lines that intersect, creating various patterns.

• Louis Frederic Wickham described fine, white or gray lines or dots on the pruritic papular rash, referred to as Wickham’s striae.

• Skin lesions are itchy and violaceous to brown papules, frequently distributed over the flexor aspect of the wrist or ankles, extensor aspect of the lower legs, skin of the lower central back, and natal clefts.

• Scalp involvement leads to hair loss (lichen planopilaris).

• Nail changes include longitudinal ridging and grooves (onychorrhexis), distal splitting (onychoschizia), separation of the nail plate from the nail bed (oncycholysis), permanent damaged nail matrix (pterygium), and permanent nail loss (anonychia).

• Koebner’s phenomenon: Lesions appear at the site of microtrauma. Mechanical trauma or irritation should be evaluated and eliminated.

Oral Manifestations

The basic lesion of OLP is a papule arranged in linear or annular forms, crisscrossing to form various patterns. Clinical forms include:

• Hypertrophic (plaque like, papular, reticular)

• Erythematous (atrophic, erosive)

• Bullous

Reticular Form

• Most common type.

• Fine, radiant, white striae known as Wickham striae, surrounded by an erythematous border.

• Commonly involves the posterior buccal mucosa, tongue, and gingiva.

• Plaque-like lesions resemble leukoplakia and appear as homogeneous white patches.

Erosive Lichen Planus

• Second most common type.

• Extensive, irregular erosions affecting the lingual and buccal mucosa, often associated with white lesions.

• Gingival involvement produces desquamative gingivitis, which has a greater potential for malignant transformation.

Pigmented Lichen Planus

• Diffuse melanosis seen along with erosive type.

• Reticular white lesions (may or may not be associated with erosive areas) surrounded by brownish to grayish-black pigmentation.

• T lymphocytes infiltrate into the basal layers, causing basal cell degeneration and stimulating melanogenesis.

• Histopathological evaluation shows basilar melanosis and melanin incontinence.

Atrophic Lichen Planus

• Diffuse red patches surrounded by white striae.

• Striae radiate peripherally at the margins of atrophic zones.

• Reticular forms are usually asymptomatic, while erosive and atrophic forms are associated with severe discomfort and burning sensation.

• Periodic evaluation for malignant transformation is necessary.

Investigations

Diagnosis is achieved by clinical presentation, complete history, and extraoral manifestations. Biopsy may be complementary.

Histopathological features include:

• Superficial band-like infiltrate of T lymphocytes

• Basal cell liquefaction and degeneration

• Normal epithelial maturation pattern

• Jagged (saw-tooth) and spindly rete ridges

• Colloid (Civatte, hyaline, cytoid) bodies

• Separation of epithelium from the lamina propria

Degeneration of basal keratinocytes and disruption of the epithelial basement membrane and basal keratinocyte anchoring elements produce weaknesses at the epithelial-connective tissue interface, resulting in histological cleft formation (Max-Joseph space) and, rarely, clinical blistering of the oral mucosa (bullous lichen planus).

Malignant Potential of OLP

The most important complication is the development of oral squamous cell carcinoma from the non-keratotic forms.

Prognosis

• Cutaneous lesions are self-limiting, and pigmentation may fade after a few years or remain permanent.

• Complete remission occurs in 70% of cases after 1 year.

• Oral lesions are chronic and rarely undergo spontaneous remission.

• Erosive oral lesions are difficult to palliate.

• Spontaneous remission of OLP is much less than 5% of patients over a 7.5-year follow-up.

• The reticular form of LP has the best prognosis because spontaneous remission occurs in 40% of cases.

• The erosive form of the lesion can persist for 15–20 years.

Management

• Reticular lesions are asymptomatic and require no therapy but only observation for changes.

• Treatment aims to eliminate atrophic and ulcerative lesions, associated symptoms, and minimize the risk of malignant transformation.

• Eliminate precipitating factors like mechanical irritants.

• Institute an optimal atraumatic oral hygiene program.

Commonly employed agents are topical corticosteroids:

• Reduce pain and inflammation.

• Examples include: Triamcinolone acetonide 0.1% in Orabase, oral suspension of triamcinolone, high potency steroid mouthwashes like betamethasone valerate 0.1%, fluocinolone acetonide 0.1%, clobetasol propionate 0.05%.

• Systemic corticosteroids are reserved for recalcitrant erosive or erythematous lichen planus or widespread involvement.

• One-third of OLP patients treated with topical steroids develop secondary candidiasis, necessitating treatment with antifungals.

Immunosuppressive and immunomodulating agents:

• Cyclosporine 100 mg/ml may be used as a mouthrinse.

• Levamisole 150 mg per day for 3 days along with prednisolone has shown excellent response and long-term remission.

• Tacrolimus is a steroid-free topical immunosuppressive agent.

Topical retinoids:

• Isotretinoin gel 0.1% acts by down-regulation of fibroblast function.

• It has been found to be of little use compared with topical steroids.

Other Treatment Modalities

• Psoralens and long wave ultraviolet A (PUVA) therapy with 8-methoxy psoralen and photochemotherapy have shown excellent results.

Surgery

• Excision, $C0_2$ laser, cryosurgery, and photochemotherapy have been effective for persistent or dysplastic lesions.

• Surgery may lead to worsening OLP via a Koebner phenomenon and reportedly causes a high rate of recurrence.

Lichenoid Drug Reaction

Lichenoid drug reactions and lichen planus exhibit similar clinical and histologic findings.

• Clinically, they demonstrate erythematous erosions and ulcerations with focal areas of radiating lines.

• Distinguished from lichen planus by association with drug administration, contact with a metal or foodstuff, or systemic disease, and their resolution when the offending agent is eliminated.

Agents causing lichenoid reactions:

• Antiarthritics, antihypertensives, antimicrobials, antiparasitics, anxiolytics, non-steroidal anti-inflammatory drugs, oral hypoglycemic agents, uricosuric agents.

Lichenoid reaction may develop after months or even years after taking the drug.

Dental materials like amalgam compounds, cobalt, gold, acrylic, and casting alloys have been known to cause lichenoid reaction.