Lichen Simplex Chronicus
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Direct answer
Lichen simplex chronicus is a localised, lichenified plaque produced by repeated rubbing and scratching of an itchy patch of skin. The itch-scratch cycle sustains it, and it typically affects the nape of the neck, wrists, ankles and anogenital skin, especially in people with atopy, chronic pruritus or prolonged stress. Treatment combines potent topical corticosteroids, used in courses, with measures that break the scratch cycle.
What you must remember
- Mechanism: an initial itch triggers scratching or rubbing, which thickens the skin, and the thickened skin itches more, so the loop sustains itself.
- Morphology: well-demarcated, lichenified plaques with accentuated skin markings, hyperpigmented or normal in colour, usually one or a few in number.
- Typical sites: posterior neck, wrists, ankles, scalp and anogenital skin, including the vulva and scrotum.
- Histology: hyperkeratosis and acanthosis with elongated rete ridges; the changes are non-specific and overlap with other lichenified disorders.
- Differential diagnosis: psoriasis, lichen planus, prurigo nodularis, lichen amyloidosis and nummular eczema.
- Underlying causes: atopic or contact dermatitis, anxiety or depression, and systemic causes of itch that must be excluded when the itch is widespread.
- Treatment: potent topical corticosteroids in courses, intralesional triamcinolone for thick plaques, topical calcineurin inhibitors for sensitive sites, and sedating antihistamines at night.
The itch-scratch cycle, step by step
Lichen simplex chronicus is best understood as a loop that the patient keeps running, and every step offers a point of intervention. A patient with a chronically itchy patch on the back of the neck is usually unaware of how often the area is rubbed.
- Trigger: a dry, irritated or atopic patch starts to itch, often after heat, sweating or contact with an irritant.
- Scratching: the patient rubs or scratches the area, frequently without awareness and especially at night.
- Thickening: repeated trauma causes hyperkeratosis and acanthosis, so the skin becomes leathery and lichenified.
- Heightened itch: the thickened skin itches more intensely, which keeps the loop turning.
- Break the cycle: treat the inflammation with a potent steroid in courses, cover the area at night to limit scratching, and address the original trigger.
- Maintain the result: after clearance, emollients and trigger avoidance reduce the chance of relapse.
Treatment works best when the early triggers are addressed, because a long-standing plaque needs prolonged therapy to clear.
Where the exam tries to catch you
Lichen simplex chronicus questions test recognition of the plaque, the differential diagnosis and the steroid regimen.
- Trap: reading a thick plaque as psoriasis Correct: psoriasis shows silvery scale and Auspitz sign, whereas lichen simplex chronicus is a localised lichenified plaque without silvery scale.
- Trap: prescribing continuous long-term steroid cream Correct: potent steroids are used in courses with step-down, because prolonged use causes atrophy and telangiectasia.
- Trap: dismissing the itch as purely psychological Correct: the itch drives the cycle, so anxiety is a contributor and treatment must target the itch as well.
- Trap: missing a systemic cause of generalised itch Correct: renal, hepatic, thyroid, iron-deficiency and haematological disorders must be excluded when itch is widespread.
Frequently asked questions
What is the itch-scratch cycle in lichen simplex chronicus?
The itch-scratch cycle is a self-sustaining loop in which itching prompts scratching, scratching thickens the skin, and thickened skin itches more. Lichen simplex chronicus is the plaque that results from this loop. Breaking the cycle is central to treatment.
Which sites are typical for lichen simplex chronicus?
The nape of the neck, wrists, ankles, scalp and anogenital skin are the typical sites for lichen simplex chronicus. These are areas the patient can reach and rub easily. A single well-demarcated plaque at one of these sites is the usual presentation.
Which steroid regimen treats thick lichen simplex chronicus plaques?
Potent topical corticosteroids applied once or twice daily in short courses, sometimes under occlusion, are the usual first choice for thick plaques. Intralesional triamcinolone is added for resistant plaques. Topical calcineurin inhibitors are preferred on sensitive sites such as the anogenital skin.
How is lichen simplex chronicus differentiated from psoriasis?
Psoriasis shows well-demarcated salmon-pink plaques with silvery scale and Auspitz sign, whereas lichen simplex chronicus has lichenified plaques without silvery scale. Lichen simplex chronicus usually appears at typical itchy sites and is linked to repeated scratching. A biopsy helps when the clinical picture remains unclear.