Lichen planus - Histology

What is Lichen Planus?

Lichen Planus is a chronic inflammatory condition that affects the skin and mucous membranes. It manifests as purplish, flat-topped papules that can cause significant discomfort. The condition is believed to be an autoimmune disorder, where the body's immune system attacks its own tissues.

Histological Features

The histological examination of lichen planus reveals several characteristic features:

Hyperkeratosis: This refers to the thickening of the stratum corneum, the outermost layer of the epidermis.
Saw-tooth rete ridges: The rete ridges, which are projections of the epidermis into the dermis, appear saw-toothed in lichen planus.
Civatte bodies: These are eosinophilic, apoptotic keratinocytes found in the lower epidermis and upper dermis.
Lichenoid infiltrate: A band-like infiltrate of lymphocytes at the dermoepidermal junction.
Basal cell degeneration: Necrosis of the basal cell layer of the epidermis.

Pathogenesis

The exact cause of lichen planus is not fully understood, but it is thought to be an autoimmune disorder. The immune system mistakenly targets the basal keratinocytes in the skin and mucous membranes. Several factors, such as genetic predisposition, infections, and certain medications, may trigger the condition.

Clinical Presentation

Lichen planus can affect various parts of the body, including the skin, oral mucosa, genital mucosa, scalp, and nails. The most common symptoms include:

Itchy, purplish, flat-topped papules
White, lacy patches in the mouth (oral lichen planus)
Painful sores
Hair loss and scalp discoloration (lichen planopilaris)
Thin, split, and ridged nails

Diagnosis

Diagnosis of lichen planus is usually clinical but can be confirmed by a skin biopsy. The histological features, as mentioned earlier, are crucial for diagnosis. Direct immunofluorescence can also be used to identify specific immune deposits along the basement membrane zone.

Treatment

There is no cure for lichen planus, but treatment aims to reduce symptoms and inflammation. Common treatments include:

Topical corticosteroids
Oral corticosteroids for severe cases
Immunosuppressive drugs
Antihistamines to reduce itching
Phototherapy

Prognosis

Lichen planus is a chronic condition that can persist for months to years. It may resolve spontaneously, but recurrences are common. Regular follow-ups and adherence to treatment are essential for managing the condition effectively.