Lichen Planus

Definition/diagnostic criteria

Lichen planus (LP) is a chronic, inflammatory, autoimmune condition that affects the skin, scalp, nails, and mucous membranes. It is characterized by polygonal, flat-topped, violaceous papules and plaques with fine scales. Wickham’s striae, a network of fine white lines, is often present on the lesions. LP may also manifest in the oral and genital mucosa.

Epidemiology

LP affects approximately 1% of the population. It is more common in adults over 40 years, and there is a slight female predominance. The aetiology is unknown, but it is thought to involve an immune-mediated process possibly triggered by certain medications, infections (hepatitis C), allergens, or stress.

Diagnosis

Clinical features

Diagnosis is primarily clinical. The typical presentation includes pruritic, purple, polygonal, planar papules and plaques, often with Wickham’s striae. Lesions are commonly found on the flexor surfaces of the wrists, legs, trunk, and oral and genital mucosa. Nail and scalp involvement may also be present. The associated itching can be intense.

Investigations

While the diagnosis of LP is usually clinical, biopsy may be necessary in atypical cases. Histopathology typically shows hyperkeratosis, acanthosis, basal cell degeneration, and a band-like lymphocytic infiltrate at the dermo-epidermal junction. Direct immunofluorescence can be used to rule out other lichenoid dermatoses. Screening for hepatitis C is recommended, particularly in patients with widespread disease or those at high risk.

Treatment

Treatment aims to relieve symptoms and minimize scarring. Mild cases may not require treatment. Topical corticosteroids are first-line therapy. Potent preparations may be necessary for thick lesions. For severe or refractory cases, systemic agents such as oral corticosteroids or immunosuppressants (methotrexate, azathioprine) may be considered.

In oral LP, topical corticosteroids are the mainstay of treatment.

Prognosis

LP is generally a self-limiting condition, but can persist for several years. Cutaneous lesions typically resolve within 18 months, but may leave hyperpigmentation. Mucosal LP tends to be more persistent and may increase the risk of squamous cell carcinoma, particularly in the oral cavity. Regular monitoring of mucosal lesions is advised.