Granuloma Annulare

Granuloma annulare (GA) is an idiopathic, generally asymptomatic, ring-shaped grouping of dermal papules which are often misdiagnosed as “ringworm.”
In very young children, GA is often self-limiting but in adults, GA tends to be more of a chronic condition and occurs in women more often than men (2.5:1).
In several case series, GA (usually generalized or chronic) has been associated with diabetes mellitus.

The cause of GA is unknown. It has been postulated that GA represents a delayed-type hypersensitivity reaction to an unknown antigen and trauma, insect bites, viral infections, and sun have all been proposed as possible triggering factors.
Familial cases of GA in identical twins and siblings suggest the possibility of a hereditary component.

Lesions are skin-colored or red firm dermal papules, with no epidermal change (scale).
Lesions may be individual isolated papules or they may be joined in annular or semiannular (arciform) plaques with central clearing (Figs. 15.7-15.9). The centers of lesions may be slightly hyperpigmented and depressed relative to their borders.
GA is generally asymptomatic and is primarily a cosmetic issue, although many patients tend to find its unexpected appearance somewhat alarming.
When localized, GA is usually self-limiting, but it may be persistent when disseminated.

Most often made clinically.
Skin biopsy will show the characteristic histopathologic features, consisting of foci of altered collagen and mucin surrounded by granulomatous inflammation with histiocytes and lymphocytes. The degenerative collagen is referred to as necrobiosis.

Differential Diagnosis

Tinea Corporis (see Chapter 18: Superficial Fungal Infections)

Erythema Migrans (Rash of Lyme Disease, see Chapter 29: Bites, Stings, and Infestations)

Annular erythematous lesion(s).
The lesion measures from 4 to 70 cm in diameter, generally with central clearing.
The center of the lesion may become darker, vesicular, hemorrhagic, or necrotic.
Lesions may be confluent (not annular), and concentric rings may form.

Cutaneous Sarcoidosis (see Chapter 34: Cutaneous Manifestations of Systemic Disease)

Annular sarcoidosis may be indistinguishable from GA.
Lesions often appear around orifices (e.g., the mouth, nose, ocular orbits) or develop in scars.

Management

The patient should be reassured of the benign nature of this condition but advised that it may be a harbinger of diabetes mellitus particularly in cases of disseminated GA.
Because GA is usually benign and self-limited, treatment may consist of clinical observation, especially if lesions are localized, asymptomatic and on nonvisible skin.
If symptomatic or of cosmetic concern, treatment with topical steroids such as class 2, high-potency fluocinonide 0.5% cream (Lidex) or super-potent class 1 clobetasol 0.05% cream may be applied. Occlusion may improve penetration. Cordran tape is another option (see “Introduction: Topical Therapy”).
Intralesional triamcinolone acetonide (Kenalog), in a dose of 2.5 to 5 mg/mL, can also be injected directly into the elevated border of the lesions with a 30-gauge needle.
Other treatments include UVA1 phototherapy, cryotherapy, and surgical excision (for localized disease).
In recalcitrant or disseminated GA, anecdotal therapeutic successes have been reported with dapsone, pentoxifylline, PUVA, adalimumab (Humira), SSKI, and narrow band UV.

Point to Remember

Distribution of Lesions

Although any part of the cutaneous surface may be involved, lesions most often arise symmetrically on the dorsal surfaces of hands, fingers, and feet (acral areas).
In adults, lesions may also be found around the elbows (Fig. 15.10) and on the trunk (Fig. 15.11).
Occasionally, GA presents as subcutaneous nodules on the arms and legs (deep or subcutaneous GA).