All too often, "ringworm" is the only diagnosis that occurs in one's mind when an annular lesion is found on physical examination. In fact, annularity is an extremely common configuration. It can be found in more than a dozen diseases spread out among several of the ten major diagnostic groups. Some of the diseases in which annular patterns are commonly seen are discussed below.

Red Papules And Nodules

Granuloma Annulare As the name suggests, annularity is an almost constant finding in this disease. In most instances complete circles are formed, but occasionally only partial circles are present. Most of the rings are 2 to 5 cm in diameter; the annulus itself is usually 3 to 5 mm wide. The rings are perfectly round except where two or more merge to form a single larger lesion with a gyrate or serpiginous border. Scale is not present. The color is usually violaceous, but pink and skin-colored lesions are sometimes seen.

Eczematous Disease

Xerotic Eczema. Annular patterns occur with some frequency in xerotic eczema. The border of such lesions is made up of a fine red line. Actually, this line is really a superficial fissure, but disruption of epithelium is so narrow that it usually cannot be visualized unless a hand lens is used. Similar narrow red fissures may crisscross throughout the patch, dividing the central area into small islands of normal-appearing skin. The lesions of xerotic eczema are usually 1 to 4 cm in diameter and are most commonly found on the lower legs and thighs. In older individuals the lesions may involve the trunk. The diagnosis is made on the basis of clinical examination.