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Diagnosing Erythematous, Eczematous Coin-Shaped Plaques on the Heel
A 34-year-old female with a medical history significant for eczema, prediabetes and liver disease presented to the clinic with a painful left medial heel wound. The remainder of her medical, surgical, medication, family, and social history was unremarkable. Per her report, the wound started out as a callus that the patient tried to remove herself; however, she was too aggressive and she related that it resulted in the painful wound. She stated she previously saw a dermatologist, who told her the lesion would resolve on its own, but months later the wound was in fact larger and more painful.
On examination the “wound” the patient referred to was actually observed to be a 3.5cm erythematous plaque with mild, thin overlying scale noted (Figure 1). She received clotrimazole 1% cream and urea 40% cream with instructions to apply both medications twice daily for 1 month, due to a suspected fungal infection. Additionally, she took time off from work, as she found being on her feet and putting pressure on the lesion caused significant pain.
The patient faithfully applied the prescribed creams for 2 months, but there was no resolution of the lesion noted. Therefore, a biopsy took place with 3cc of 0.5% bupivacaine plain local anesthesia and iodine paint prep. A 3mm punch biopsy was performed and sent to a dermatopathologist in formalin. The foot dressing included petrolatum-impregnated non-stick gauze, gauze pads, a gauze roll, and a mildly compressive elastic wrap as there was a moderate amount of bleeding. However, the patient was instructed to use a topical antibiotic ointment and regular adhesive bandage on it in a couple of days after rinsing it with mild soap and water in the shower.
The pathology report described volar skin with slight spongiosis and focal parakeratosis with a perivascular mononuclear infiltrate (Figure 2). A periodic acid-Schiff stain was negative for fungal organisms. The patient was encouraged to continue applying the urea 40% cream, but was also prescribed clobetasol 0.05% ointment in place of the clotrimazole. In fact, the patient was encouraged to apply emollient lotion regularly and indefinitely, especially during the dry winter months. Within a few weeks the patient found resolution of her pain and the problematic lesion, and was able to return to work.
Key Questions To Consider
1. What is the diagnosis?
2. What are the key findings in this disease?
3. What is the treatment of choice?
4. What does the prognosis entail for these patients?
Answering The Key Diagnostic Questions
1. Nummular eczema
2. Erythematous, eczematous coin- shaped plaques usually occurring on the extremities
3. Topical steroids and good skin care—ie, lotion, and gentle soaps
4. Usually chronic with a relapsing/remitting course
What You Should Know About Nummular Eczema
In this case, the patient’s diagnosis was nummular eczema. Eczema is the most common inflammatory skin disease in existence, and it comes in many forms. It involves various manifestations of skin irritation depending on whether the disease is acute, subacute or chronic. These manifestations may include vesicles, blisters, erythema, scaling, fissuring, lichenification, excoriations and more.1
Nummular eczema specifically was originally described in the mid-1800s by Devergie.2 It can present in any of the three stages (ie, acute, subacute or chronic) but usually takes the form of multiple coin-shaped erythematous plaques that are symmetrically distributed—and vary from 1 to 10 cm in size. Although these coin-shaped erythematous plaques do have an overlying scale, it is thin and sparse compared to the thick, silvery scale of psoriasis.1 The lesions are often pruritic and can be quite intensely so, resulting in scratching and excoriations as well as abrasions and even lacerations. It usually appears on the extremities, but debate exists as to whether it shows up more on the upper or lower extremities.2,3 The middle-aged and elderly are more affected, especially during the winter months due to the drying effect of the cold winter air as well as the more frequent use of hot water, soaps and detergents.2 While nummular eczema usually follows a chronic course, infrequently it will resolve after a few months.
The cause of nummular eczema is unknown, but it seems to be multifactorial with potential contributors including environmental, allergic, emotional, and nutritional.2 It is associated with other conditions such as xerosis, chemical exposure, stasis dermatitis and allergic contact dermatitis. In fact, nummular eczema occurs concurrently with allergic contact dermatitis in over 30% of patients; therefore, patch testing is recommended to determine the offending allergens and aid in resolution of the allergic response and skin irritation.4 A study in 2012 by Bonamonte and colleagues confirmed that 332 of 1022 patients with nummular eczema (32.5%) reacted to one or more allergens, with the most common offending agents being nickel sulfate (10.2%), potassium dichromate (7.3%) and cobalt chloride (6.1%).5
The differential diagnosis for nummular eczema includes psoriasis, tinea corporis, autoeczematization, cutaneous T-cell lymphoma (CTCL), contact dermatitis, atopic dermatitis and pigmented purpura, along with xerosis and stasis dermatitis as mentioned above.4 Although the diagnosis is mainly clinical due to the characteristic appearance and symptoms, various diagnostic tests can be utilized to confirm the diagnosis if the lesions are atypical or if there are confounding factors. For example, a potassium hydroxide wet-mount examination of skin scrapings can be performed to rule out fungal infection/tinea.3 Dermoscopy is another non-invasive method of diagnosis and will show scales, shiny yellow clods and irregularly distributed brownish-red globules.6 A biopsy of the lesion may be performed if all else fails, although there are no specific findings for nummular eczema—histology will show characteristics common to many forms of eczema, including spongiosis, parakeratosis, acanthosis, eosinophils and exocytosis of lymphocytes.7 Combined with the appearance and symptoms, however, a biopsy can be quite helpful, especially when tinea corporis is suspected.
Understanding Treatment Options and Prognosis
Click here for a Table that lists treatment options.
Initial management of nummular eczema involves avoidance of precipitating factors and allergens, and optimal skin care. Intuitively, if patch testing shows reactivity to a certain allergen, avoiding the offending allergen will help with skin inflammation and may allow for complete resolution. Bathing in hot water and using harsh soaps should be avoided due to the drying, damaging effect on the skin. Patients should moisturize their skin frequently as dry skin tends to get irritated more easily, and there are multiple options depending on patient preference and tolerability. For example, ointments and emollient creams (ie, petrolatum, vegetable shortening and coconut oil) are the most effective vehicles for skin moisturization due to their high lipid concentrations, lower water content and fewer allergens.4 Thus they cause less irritation and stinging upon application and are more occlusive, allowing less water loss from the skin. However, increased greasiness causes less adherence with these vehicles, so other formulations have been introduced that allow for quicker drying and less messiness, such formulations including foams, lotions, gels and liquids. While easier and cleaner to use, these other vehicles sacrifice water loss and thus have decreased moisturization capability.
If patients continue to experience symptoms despite avoidance of triggering factors and optimal skin care, there are many non-steroidal options that can help achieve resolution if physicians don’t want to skip right to steroids. For example, moisturizers with pramoxine 1% may be as antipruritic as hydrocortisone 1% cream. Antihistamines, whether they be H1 or H2 receptor antagonists, can help with pruritus and thus the secondary lesions like excoriations. Cannabinoids are showing promise against pruritus, although they lack significant randomized controlled trials. Topical calcineurin inhibitors, including tacrolimus (Protopic, Astellas Pharma) and pimecrolimus (Elidel, Meda Pharma) are another effective alternative to steroids in decreasing skin inflammation, although their cost can be quite prohibitive. Dupilumab resulted in improvement lasting at least 120 days in one case series.4
Other less-frequently used treatments include crisaborole (Eucrisa, Pfizer), tar, phototherapy, systemic cyclosporine, azathioprine, methotrexate, and mycophenolate mofetil (CellCept, Roche).4
The mainstay of therapy for nummular eczema is topical corticosteroids, which are safe for daily administration for up to several weeks at a time and for long-term intermittent use. Once a day dosing is sufficient, as beyond that, corticosteroid receptors are saturated and additional applications therefore will only provide an emollient effect.4 Group 1 to 3 steroids are appropriate to use on the legs and feet. A more comprehensive list of topical steroids, non-steroidal preparations and over-the-counter medications is included in the table online.
Of course, oral or intralesional steroids may be utilized if topicals are not producing the desired result. Intralesional triamcinolone acetonide 2.5 to 5 mg/mL injected every 3-4 weeks can be used for thicker lesions. Additionally, prednisone 0.5 to 1 mg/kg orally daily can help with more generalized flares or diffuse dermatitis, but must be tapered over 2-3 weeks.4 With proper treatment, nummular eczema will resolve over the course of a few weeks, but one should be prepared for relapses, as the course can be chronic.
Final Thoughts
Nummular eczema, a coin-shaped eczematous lesion mainly found on the extremities, usually presents on elderly patients in the winter; however, it can present at any age and at any time. Diagnosis is usually clinical, but dermoscopy, skin scrapings and even a biopsy can be helpful in confirming or ruling out other pathologies. Treatment consists of avoidance of triggering factors and good skin care, along with topical steroids as needed. Although an acute flare will usually resolve within a few weeks, the course can be chronic with relapses and remissions.
Dr. Vella is a fellowship-trained podiatrist who practices in Gilbert and Sun City, AZ.
References
1. Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. (5th ed). Mosby Elsevier; 2010.
2. Halberg M. Nummular eczema. J Emerg Med. 2012;43(5):327-328.
3. Leung AKC, Lam JM, Leong KF, et al. Nummular eczema: an updated review. Recent Pat Inflamm Allergy Drug Discov. 2020;14(2):146-155.
4. CX Chan, Zug KA. Diagnosis and management of dermatitis, including atopic, contact and hand eczemas. Med Clin N Amer. 2021;105(4):611-626.
5. Bonamonte D, Foti C, Vestita M, et al. Nummular eczema and contact allergy: a retrospective study. Dermatitis. 2012;23(4):153-157.
6. Suh KS, Park JB, Yang MH, et al. Diagnostic usefulness of dermoscopy in differentiating lichen aureus from nummular eczema. J Dermatol. 2017;44(5):533-537.
7. Robinson CA, Love LW, Farci F. Nummular dermatitis. StatPearls Publishing;2022.
8. Vlahovic TC, Schleicher SM. Skin Disease of the Lower Extremities: A Photographic Guide. HMP Communications;2012.
