Lichen planus is a chronic inflammatory disease that affects the skin, mouth (oral mucosa), nails, scalp, and sometimes genitals. It is considered an autoimmune-related condition, where the immune system attacks the skin or mucous membranes.

🔎 Key Features (Classic Exam Points)

Remember the “6 P’s”:

• Pruritic (itchy)

• Purple

• Polygonal

• Planar (flat-topped)

• Papules

• Plaques

Also:

• Wickham striae → fine white lacy lines on lesions (especially oral type)

📍 Common Sites

• Flexor surface of wrist

• Ankles

• Lower back

• Oral cavity (inside cheeks)

• Genitals

• Nails (can cause thinning, ridging, pterygium)

• Scalp (called Lichen planopilaris → may cause hair loss)

🧬 Causes

Exact cause unknown, but associated with:

• Autoimmune mechanism (T-cell mediated)

• Stress

• Hepatitis C infection

• Certain drugs (NSAIDs, beta blockers, antimalarials)

• Dental materials (oral LP)

🩺 Symptoms

Skin:

• Itchy, shiny, flat-topped purple bumps

• May leave hyperpigmentation after healing

Oral:

• White lacy patches (usually painless)

• Painful ulcers in erosive type

• Burning sensation while eating spicy food

Nail:

• Longitudinal ridges

• Nail thinning

• Nail loss (severe cases)

🔬 Diagnosis

• Clinical appearance

• Skin biopsy (if unclear)

• Screening for Hepatitis C (sometimes advised)

💊 Treatment

There is no permanent cure, but it is manageable.

First-line:

• Topical corticosteroids (Clobetasol)

Severe cases:

• Oral steroids

• Tacrolimus ointment (oral LP)

• Antihistamines (for itching)

• Phototherapy

⏳ Prognosis

• Skin lesions usually resolve in 6–18 months

• Oral lichen planus may persist longer

• Recurrence possible

⚠ Oral lichen planus has a small risk of malignant transformation → Regular follow-up required.