The FP made the presumptive diagnosis of nummular eczema, but recognized that a fungal infection and psoriasis were part of the differential diagnosis. He performed a potassium hydroxide (KOH) preparation, which was negative for hyphae and fungal elements. (See a video on how to perform a KOH preparation here: http://www.mdedge.com/jfponline/article/100603/dermatology/koh-preparation.) In order to explore whether this might be a case of guttate psoriasis, the FP asked about any preceding strep pharyngitis or other respiratory infections. The patient, however, had not had any preceding infections. The FP also checked her nails, scalp, and umbilicus for other signs of psoriasis, but found none. The FP was now confident in making a clinical diagnosis of nummular eczema (also known as nummular dermatitis).
Nummular eczema is a type of eczema characterized by circular or oval-shaped scaling plaques with well-defined borders. (“Nummus” is Latin for “coin.”) Nummular eczema produces multiple lesions that are most commonly found on the dorsa of the hands, arms, and legs.
Patients who have a history of atopic dermatitis are more likely to get nummular eczema even after they outgrow the atopic dermatitis. The 2 conditions involve problems with the barrier function of the skin, and emollients are helpful for the prevention and treatment of both.
In this case, the FP prescribed 0.1% triamcinolone ointment to be applied twice daily until the lesions resolved. At a one-month follow-up appointment, the patient indicated that her legs were now smooth and she was happy that she could shave them again. The FP told her that it would be a good idea to use emollients after bathing to keep the skin moist in order to prevent future episodes of nummular eczema.
Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Wah Y, Usatine R. Eczema. In: Usatine R, Smith M, Mayeaux EJ, et al, eds. Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw-Hill; 2013.
To learn more about the Color Atlas of Family Medicine, see: www.amazon.com/Color-Family-Medicine-Richard-Usatine/dp/0071769641/
You can now get the second edition of the Color Atlas of Family Medicine as an app by clicking on this link: usatinemedia.com