Round Pruritic Plaques

A 24-year-old white male complains of highly pruritic plaques scattered over his lower extremities of a 6-week duration. The plaques are not painful. He is unsure whether they all appeared at once or if 1 lesion appeared and spread. Initially, erythematous papules were scattered throughout the plaques, which then progressed to form scale and crusting. Nothing seems to exacerbate the plaques, though pruritus is worse at night. The patient used over-the-counter topical hydrocortisone which mildly diminished the pruritus but did not clear the plaques. He denies fever and fatigue. 

History. His past medical history is unremarkable. He is not taking any medications. 

Physical examination. The patient had 4 to 6 coin-shaped plaques per leg, ranging in size from 2 cm to 4 cm. Crust and fine scale are present throughout the plaque, without central clearing. 

Discussion. Nummular eczema is a chronic relapsing inflammatory skin disorder of unknown etiology. Lesions are typically highly pruritic, coin shaped, and often characterized by an erythematous exudative plaque with crust in the early stages and a dry plaque with thin scale in later stages. Plaques are most commonly found on the extremities and lower trunk, and worse in winter months. 

While nummular eczema may occur at any age, the highest incidence occurs in young adulthood and in older adults.^1,2 Many aggravating factors have been implicated, including alcohol, aeroallergens, and emotional stress.^3,4 

Differential diagnosis. Nummular eczema is often mistaken for tinea or psoriasis. Tinea will have scale and vesicles at the border, termed the active border, with central clearing of the plaque. The plaque in nummular eczema will have scale and vesicles scattered throughout the plaque without central clearing. Psoriasis will have a thicker silvery scale. Diagnosis is made clinically but a KOH preparation and biopsy will help distinguish between a dermatophytosis and psoriasis.^1,2 

Research. In a retrospective study, allergic contact dermatitis was found to be associated with nummular eczema, thus if recalcitrant disease, patch testing should be performed.³ First line treatment consists of high potency topical steroids applied twice daily until lesions clear. Intralesional triamcinolone is often injected into individual lesions. A moisturizing cream daily and after bathing is also recommended. Phototherapy, cyclosporine, and oral retinoids are used in difficult cases.⁵ Concomitant infection with S. aureus is common and if present should be treated with systemic antibiotics. Lesions may be difficult to treat, lasting weeks to months with eventual clearing, unfortunately recurrence is common.^1,2

REFERENCES:

1.Habif, TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 5th ed. Philadelphia, PA: Elsevier, Inc; 2009:707-708. 

2.Johnson RA, Saavedra A, Wolff K. Fitzpatrick’s Color Atlas and Synopsis of Clinical Dermatology. 5th ed. New York, NY: McGraw-Hill; 2005. 

3.Bonamonte D, Foti C, Vestita M, et al. Nummular eczema and contact allergy: a retrospective study. Dermatitis. 2012;23(4):153-157. 

4.Jiamton S, Tangjaturonrusamee C, Kulthanan K. Clinical feature and aggravating factors in nummular eczema in Thais. Asian Pac J
Allergy Immunol. 2013;31(1):36-42. 

5.Coenradds PJ. Hand eczema. New Engl J Med. 2012;367:
1829-1837.