Lichen Simplex Chronicus

Lichen simplex chronicus (LSC), or neurodermatitis, is a localised, chronic, lichenified eczematous plaque resulting from repeated rubbing and scratching (the itch scratch cycle).

• Affects 12% of the population at some time; peak at 30 to 50 years; women more than men.
• Underlying triggers: atopy, anxiety, depression, obsessive compulsive traits, insect bites, dermatitis, xerosis, venous insufficiency, neuropathy (notalgia paraesthetica, brachioradial pruritus), and genital conditions (lichen sclerosus, candidiasis).
• Sites: nape of neck, scalp, ankles, wrists, extensor forearms, vulva, scrotum, and perianal skin.
• Chronic itch markedly impairs sleep and quality of life.

• Well defined, thickened plaque with exaggerated skin markings, hyperpigmentation, excoriations, and scaling.
• Intense paroxysmal itch, worse at night or when relaxed, and relieved by scratching.
• Hair loss, nodular prurigo form (multiple nodules), and genital variants (labial thickening, "white" lichenified skin).

• Clinical diagnosis.
• Biopsy for refractory or atypical lesions (acanthosis, hyperkeratosis, hypergranulosis, vertical collagen streaks).
• Patch testing for suspected contact allergy; skin scrapings (KOH) for tinea; swabs for infection.
• Check ferritin, thyroid, renal and liver function, HbA1c, and HIV in generalised itch.
• Exclude psoriasis, lichen planus, tinea, lichen sclerosus, extramammary Paget disease, squamous cell carcinoma in situ (especially genital lesions), and prurigo nodularis.

• Break the itch scratch cycle: short nails, night time gloves or occlusion, cool compresses, and psychological support (habit reversal).
• Potent to super potent topical steroid: clobetasol propionate 0.05% ointment once or twice daily for 2 to 4 weeks, then taper; occlude with hydrocolloid dressing or flurandrenolide tape.
• Intralesional triamcinolone 5 to 10 mg/mL into the plaque every 3 to 4 weeks for resistant lesions.
• Calcineurin inhibitors: tacrolimus 0.1% ointment, pimecrolimus 1% cream.
• Night sedation: hydroxyzine 25 to 50 mg, doxepin 10 to 25 mg, amitriptyline 10 to 50 mg.
• Neuromodulators: gabapentin 300 to 900 mg three times daily or pregabalin 75 to 150 mg twice daily; topical capsaicin 0.025 to 0.075%, topical doxepin 5%, or lidocaine 5%.
• Prurigo nodularis: dupilumab 600 mg then 300 mg every 2 weeks, nemolizumab.
• Treat underlying atopy, infection, and mood disorder; narrow band UVB or cryotherapy for stubborn plaques.