Lichen Simplex Chronicus
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This itchy rash on the nape of a 25-year-old woman’s neck had been present for several months; it had resisted treatment with antifungal cream and shampoo. The patient had a history of atopic phenomena, including asthma, eczema, and urticaria as a child, and seasonal allergies as an adult. There was no family history of psoriasis but a strong history of atopy. The patient admitted that she scratched this rash often and vigorously.
Examination revealed a 7 3 3 cm pink patch with a leathery, slightly scaly surface on the nuchal scalp. No lymph nodes were palpable in the area. There were no rashes on the elbows, knees, or remainder of the scalp. The nails were free of pits, onycholysis, and spotting. No nits were visible in the hair.
Lichen simplex chronicus (LSC), which is also known as neurodermatitis, was diagnosed. LSC almost always starts with focal pruritus, which can be from any number of causes: contact or irritant dermatitis, xerosis, psoriasis or, as in this case, eczema.
The thickening of the skin (lichenification) is a reaction to the chronic scratching and rubbing, which also leads to hypersensitivity of surface sensory nerves. The result is the initiation of a self-perpetuating itch-scratch-itch cycle, which must be broken with the judicious use of topical corticosteroid creams—in this case, betamethasone—and strict instructions for the patient to leave the area alone.
LSC is often misdiagnosed as a fungal infection. Although it was in the differential in this case, a fungal infection was unlikely given the failure of topical antifungals, the absence of reactive lymph nodes in the area, and the nuchal location, which is unusual for tinea capitis; however, it is the classic location for LSC in women.