What is lichen simplex?
Lichen simplex is a localised area of chronic, lichenified eczema/dermatitis. There may be a single or multiple plaques. It is also called neurodermatitis.
What causes lichen simplex?
Although the mechanism is not understood, lichen simplex follows repetitive scratching and rubbing, which arises because of chronic localised itch. The primary itch can be due to:
- Atopic eczema
- Contact eczema
- Venous eczema
- Lichen planus
- Fungal infection
- Insect bite
- Neuropathy (radiculopathy) eg, brachioradial pruritus.
Itch due to neuropathy appears to be due to hyperexcitable sensory nerve fibres following nerve injury or entrapment.
Who gets lichen simplex?
Lichen simplex occurs in adult males and females. It is unusual in children. It is more common in people with anxiety and/or obsessive compulsive disorder.
What are the clinical features of lichen simplex?
A solitary plaque of lichen simplex is circumscribed, somewhat linear or oval in shape, and markedly thickened. It is intensely itchy. Other features may include:
- Exaggerated skin markings
- Dry or scaly surface
- Leathery induration
- Broken-off hairs
- Scratch marks.
Lichen simplex is often solitary and unilateral, usually affecting the patient’s dominant side. Multiple plaques can also arise, with bilateral and symmetrical or asymmetrical distribution. The location of lichen simplex is not random, as some body sites are particularly commonly affected. These include:
- Back of scalp and neck
- Wrists and forearms
- Lower legs.
How is lichen simplex diagnosed?
Clinical appearance is generally typical. At times, it may be helpful to do some investigations. These would include:
In the absence of known underlying skin problem or infection, consider neuropathy. Is there a history of spinal injury, disease or symptoms? In severe cases, the following tests may be performed (although they are often unhelpful):
- Spinal imaging: X-rays, CT scans, MRI scans
- Electrophysiological nerve conduction studies.
What is the treatment for lichen simplex?
It is important to understand that the itchy patch of skin is, at least in part, due to scratching and rubbing. Treatment needs to address the symptoms and any underlying cause.
Treatment of the lichen simplex may include:
- Potent topical steroids until the plaque is resolved (4–6 weeks) — occlusion for a few hours after application may enhance efficacy
- Reduce potency or frequency of topical steroids once lichenification has resolved
- Steroid injections every 4–6 weeks
- Coal tar preparations
- Moisturisers to relieve dryness and reduce desire to scratch
- Cooling creams containing menthol
- Antihistamine or tricyclic antidepressant (eg, amitriptyline or nortriptyline), to help sleep.
The primary condition needs treating; for example:
- Antifungal agents for dermatophyte infection
- Phototherapy and immunomodulatory medications for inflammatory dermatoses (oral corticosteroids, methotrexate, azathioprine or ciclosporin)
- Tricyclic antidepressants (amitriptyline, nortriptyline, doxepin), other antidepressants (eg, duloxetine) or antiepileptic medications (valproate, lamotrigine, gabapentin) for radiculopathy.