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AT-A-GLANCE

AT-A-GLANCE

Nummular eczema:

  • Also known as nummular dermatitis and discoid eczema.

  • A chronic inflammatory skin disorder of unknown etiology.

  • Papules and papulovesicles coalesce to form nummular plaques with oozing, crust, and scale.

  • Most common sites of involvement are upper extremities in men and women, particularly the dorsal hands in women, and the lower extremities in men.

  • Pathology may show acute, subacute, or chronic eczema.

Lichen simplex chronicus

  • A chronic, severely pruritic disorder characterized by one or more lichenified plaques.

  • Most common sites of involvement are scalp, nape of neck, extensor aspects of extremities, ankles, and anogenital area.

  • Pathology consists of hyperkeratosis, hypergranulosis, psoriasiform epidermal hyperplasia, and thickened papillary dermal collagen.

Prurigo nodularis

  • Also known as prurigo, picker’s nodules, or nodular prurigo of Hyde.

  • A pruritic disorder that runs a chronic course.

  • Hyperkeratotic firm nodules vary in size from 0.5 to 3.0 cm and may be excoriated.

  • Associations include atopic dermatitis and systemic causes of pruritus.

  • Pathology consists of hyperkeratosis, hypergranulosis, psoriasiform epidermal hyperplasia, thickened papillary dermal collagen, and characteristic neural hypertrophy.

This chapter discusses the evaluation and management of nummular dermatitis, lichen simplex chronicus, and prurigo nodularis. These disorders are each associated with intense itch and characteristic morphologic findings. Each of these disorders may present in patients with atopic and contact dermatitis. However, these disorders often present in the absence of atopic disease and may be associated with underlying systemic disease.

NUMMULAR ECZEMA

Nummular eczema or discoid eczema is a morphologic term to describe coin-shaped plaques that may have multiple etiologies. The term was first coined by Devergie in 1857.1 Nummular lesions are commonly observed in atopic dermatitis (AD), and may have a predilection for school-age children with AD2,3 and adult-onset AD.4 A large proportion of patients with nummular eczema have underlying allergic contact dermatitis.5,6

However, some use this term to describe a specific diagnosis, which excludes other common dermatoses presenting with nummular lesions.7 The epidemiology of nummular eczema is not well-defined, in part owing to the different definitions used in studies. Prevalence estimates for nummular eczema were found to be 1 to 2 per 1000 population in studies of the populations of the U.S. in 19788 and Sweden in 1969.7 Nummular eczema was encountered in 2.2% of dermatologic visits in Turkey in 2011-2012.9 Nummular eczema is more common in adults, with multiple observed peak ages-of-onset at 15-25,7,8,10 50-59,7,10 and 65-74 years.7,8 Previous studies found conflicting results about whether nummular eczema is more common in adult males7 or adult females.8 No racial or ethnic predilection for nummular eczema has been demonstrated.

ETIOLOGY AND PATHOGENESIS

The pathogenesis of nummular eczema appears to be multifactorial. Many of the proposed triggers of nummular eczema overlap with those of AD, ...

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