Psariasis

Annular patterns are particularly likely to be found in psoriasis when individual lesions undergo resolution. In such a situation the central portion of a plaque fades, leaving an erythematous border at the periphery. This border is generally wider (5 to 8 mm) than that found in the other annular diseases, and there is a tendency for the border to break up into individual papules. The size of the annular lesions and their configuration depend on the appearance of the plaque that preceded them. Since annularity usually occurs during resolution, centrifugal growth is not commonly seen. Typical psoriatic scale is usually present on the border, but when the disease is under active treatment, the formation of scale is minimal or absent. Diagnosis is not ordinarily difficult, since more typical lesions of psoriasis can be found elsewhere on the body.

Tinea Corparis

Annular lesion's are found in Microsporum. sp. infections of children and in TrichoPhyton rubrum. infections of adults. In children the lesions are solitary or are few in number. They are usually only 2 to 4 cm in diameter and are generally found on exposed surfaces. Complete circles are formed, and there is relatively little tendency for coalescent growth of adjacent lesions. Scale is always present at the active border. The amount of inflammation and thus the intensity of the redness are highly variable. Potassium hydroxide (KOH) preparations, fungal cultures, or both should be carried out to confirm a clinical diagnosis.

The annular lesions of tinea corporis in adults are quite different. Larger rings are noted, and coalescent growth frequently results in the development of very large lesions with serpiginous borders. Complete circles are not often found, and in fact, gaps in the ring-like border may be large enough to interfere with recognition of the annular pattern. The active, advancing border is quite narrow (1 to 3 mm) and is usually scaling. Postinflammatory hyperpigmentation may be found within the central portion of the lesions as centrifugal growth occurs. New circles can sometimes redevelop in the cleared central area of the larger rings. Tinea corporis in the adult usually begins on the upper, inner thighs and from there extends onto the buttocks and lower trunk around the belt line. Less commonly, the face or dorsal surface of the hands may be involved. The disease is pruritic, and excoriations (fungal eczema) are often present. KOH preparations, fungal cultures, or both should be used to confirm a clinical diagnosis.

Lupus Erythematosus

The lesions of discoid Lupus Erythematosus (LE) regularly assume an annular configuration when the central portions of otherwise-solid plaques begin to undergo resolution. This resolution often results in the development of hypopigmentation and scarring in the central area. The presence of scarring is a pathognomonic feature of discoid LE. Some of these annular plaques are stable in size, while others show evidence of very slow centrifugal growth. The active border is usually thin, with some evidence of scale formation. Most lesions are 2 to 5 cm in diameter. Lesions are most often found on the face, scalp, and neck, but occasionally the upper trunk and arms are involved. A clinical diagnosis can be confirmed by biopsy.

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