The yellow clod sign.

N UMMULAR OR DYSREGULATIVE MICRObial eczema, which is a subtype of chronic dermatitis, is characterized by coin-shaped, sharply demarcated, erythematous lesions with serous exudates demonstrated on dermatopathologic examination. 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, excoriations, or basal cell carcinomas, form reddish crusts instead.