Answer: D

Lichen simplex chronicus (LSC), also referred to as circumscribed neurodermatitis, is a condition characterized by an “itch-scratch” cycle in which patients repeatedly scratch affected areas, resulting in skin thickening.1,2 Vidal coined the term lichen simplex chronicus in 1886 and Brocq expanded the description of the condition in 1891.3

The condition is estimated to affect 12% of the population, with a peak incidence among adults 30 to 50 years of age.4 It is approximately 2 times more common in women.4 The incidence of LSC is reported to be higher among people of Asian descent.2 The disorder is linked to other conditions including eczema, hay fever, asthma, and anxiety disorders.5,6 Psychological factors such as stress, anxiety, depression, and obsessive-compulsive disorder are thought to trigger LSC.2,4

The thickening of the skin in LSC arises because of to repeated scratching and rubbing of a pruritic area, which may begin to itch spontaneously or secondary to an underlying condition. The cause of pruritus may be a medical condition such as obstructive biliary disease or chronic renal disease, or a skin condition such as eczema, allergic contact dermatitis, insect bites, psoriasis, or xerosis.3,4,7 Pruritus in LSC also has been linked to nerve regrowth because of repeated mechanical trauma from scratching.3 Psychological factors also may be related to pruritus and scratching may serve as a way to relieve emotional stress and tension; however, the resultant plaques tend to lead to more stress and itching.3,4 The pruritus in LSC may be so intense that it disturbs sleep.5

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A patient can have a single or multiple LSC plaques that appear well-circumscribed and lichenified and may have associated scale. The lesions also can have excoriations from excessive scratching.2,4,5 Both hyper- and hypopigmentation may occur, although brown or dusky violaceous hyperpigmentation is more common. Pigment changes can be more significant in patients with darker skin tones.2 Plaques may occur anywhere on the body but are more common in areas that are easy to reach, such as the head, the sides and nape of the neck, extensor surfaces of the arms and lower legs, ankle flexures, genitals (vulva, scrotum), anus, and inner thighs.2,4

Histopathologic findings in LSC include epidermal hyperplasia with acanthosis, dermal fibrosis, and vertically streaked collagen bundles.2 Orthokeratotic hyperkeratosis, regular elongation of rete ridges, hypergranulosis, and perivascular infiltrate of lymphocytes or macrophages also may be observed in addition to eosinophils in the superficial dermis.1,4 Histologic features can be more difficult to interpret if LSC is superimposed on areas of skin affected by other diseases, such as psoriasis. In these cases, the patient may present with histologic and clinical findings of both conditions.2

Diagnosis of LSC is based on clinical features.2 Clinical evaluation includes a history and physical examination, symptoms reported by the patient, and dermoscopic evaluation. Additional testing is necessary only to rule out other diagnoses or to investigate for underlying systemic disease.2,4 When an underlying condition is suspected, appropriate tests include a complete blood cell count, metabolic panel, kidney and liver function tests, and thyroid function tests.3

Psoriasis, lichen planus, contact dermatitis, mycosis fungoides, and tinea corporis are disorders that mimic LSC. These conditions often can be differentiated from LSC by distribution and morphology, but additional tests occasionally are needed.2 Patch testing can help exclude contact dermatitis and biopsies can help differentiate LSC from mycosis fungoides and psoriasis. In cases with genital involvement, potassium hydroxide preparation or fungal cultures may aid the differentiation from candidiasis and tinea infections.4

In general, treatment of LSC can be difficult and relapses are frequent.2 To treat LSC, a practitioner first should consider whether an underlying condition may be the cause of the patient’s pruritus.5 In the absence of an underlying condition, it is necessary to break the itch-scratch cycle.5 Patients are counseled to resist scratching and apply a cold pack or ice to help soothe the area.2 Simple measures to minimize skin irritation include avoidance of excessive washing, harsh soaps, and rough clothing.

Topical corticosteroids of moderate or high potency are first-line treatments and can be administered under occlusion.2-5 Topical emollients also may be used.4 For nocturnal pruritus, a sedating antihistamine such as hydroxyzine may prove helpful in some patients.2,5 For cases with a psychological etiology, reduction of stress and anxiety through lifestyle modification, psychotherapy, and/or medication may be effective.2,4 In more persistent cases, corticosteroid or botulinum toxin injections can be considered.2,4 Especially severe cases may warrant surgical removal of localized lesions.4

For the patient in this case, the condition was diagnosed clinically. The patient was counseled extensively about the itch-scratch cycle and the importance of avoiding further scratching and trauma to the area. He was prescribed potent topical corticosteroids. Over several months, the patient’s lesion became thinner and less itchy.

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