Diagnosis: Lichen simplex chronicus
This patient was given a diagnosis of lichen simplex chronicus (circumscribed neurodermatitis)—pathohistologic changes to the skin caused by habitual trauma from scratching a single area. The lesion begins as small red papules that later coalesce into a plaque with furrows (lichenification).1 The plaques become well circumscribed with attenuated skin lines. This is due to the thickening of both the epidermis (acanthosis) and stratum corneum (hyperkeratosis).2 Hyperpigmentation or hypopigmentation may be present—particularly in patients with naturally dark-colored skin.1
The epidemiology of lichen simplex chronicus is unknown. It tends to occur in adults between 30 and 50 years of age (although it has been seen in children) and is more common in women and people of Asian descent.3 The areas of the body that are affected are those that are easily reached, including the:4,5
- outer portion of the lower legs
- scrotum and vulva; pubic and anal areas
- wrists and ankles
- upper eyelids
- back or side of neck
- ear canal
- extensor forearms near the elbow
- fold behind the ear
- scalp
Pathology will show lichenification, acanthosis, hyperkeratosis, and eczematous inflammation resembling psoriasis. The histologic separation between lichen simplex chronicus and psoriasis is particularly difficult, which leads some pathologists to report the process as “psoriasiform dermatitis.”1 That was the case in this presentation.
Differential diagnosis includes lichen planus, psoriasis
Skin conditions with a similar appearance to lichen simplex chronicus include lichen planus, lichen sclerosus, psoriasis, mycosis fungoides, and extramammary Paget’s disease.1,2,4,5
Lichen planus is an inflammatory cutaneous lesion of unknown etiology. It can be found throughout the body, including the mucous membranes. It commonly presents as the 5 Ps: pruritic, planar, polyangular, purple, and papules.5 Upon close examination, Wickham’s striae (reticular white lines) may be visible.4,5