An Annular Eruption on the Trunk and Limbs

A man in his 20s presented with a 2-month history of itchy skin lesions on his trunk, arms, and groin. He was otherwise healthy, with no other underlying conditions, and he was taking no medications. He had no history of atopic dermatitis or other eczematous dermatoses. There were no associated extracutaneous symptoms. His family medical history was relevant only in that his mother had systemic lupus erythematosus. On physical examination, there were several erythematous annular patches on the abdomen (flanks and periumbilical region), lower back, groin, wrists, and legs (Figure, A). The lesions showed slightly raised red-brown borders and a clear center in some patches with no visible scaling, hypopigmentation, induration, or atrophy. Results of laboratory studies including complete blood cell count, biochemical analysis, complement levels, antinuclear antibodies, anti-Ro, anti-La, anti-ribonucleoprotein, anti-Smith, and anti-dsDNA antibodies, as well as serologic testing for syphilis and hepatitis B and C virus, were all normal or negative. A punch biopsy specimen was obtained for histopathologic evaluation (Figure, B and C).