Nummular or dysregulative microbial eczema, which is a subtype of chronic dermatitis, is characterized by coin-shaped, sharply demarcated, erythematous lesions1,2 with serous exudates demonstrated on dermatopathologic examination.3 These serum exudates can be seen dermoscopically as shiny yellow clods with a diameter of 1 to 2 mm. The closest differential diagnoses, which are psoriasis and tinea corporis, typically do not have them. Figure 1 (upper inset) shows a roundish nummular eczema with multiple yellow clods (Figure 1, original magnification ×10) on the calf of a 51-year-old man. Other dermoscopic features of nummular eczema are evident on the back of the hand of a 76-year-old man (Figure 2). These clods are not visible without immersion fluid but are readily identifiable when the lesion is prewetted. Figure 1 (lower insert) shows a hematoxylin-eosin –stained biopsy specimen of the serum crust seen in Figure 1. Bleeding lesions, such as pyogenic granulomas,4 excoriations, or basal cell carcinomas, form reddish crusts instead.
Navarini AA, Feldmeyer L, T öndury B, Fritsche P, Kamarashev J, French LE, Braun RP. The Yellow Clod Sign. Arch Dermatol. 2011;147(11):1350. doi:10.1001/archdermatol.2011.297