Granuloma Annulare

Elyse M. Love

Evan Rieder

BACKGROUND

Granuloma annulare (GA) is a common noninfectious, inflammatory condition that results from focal degeneration of elastic fibers. Two-thirds of patients are less than 30 years of age at presentation. Incidence is twice as common in females as in males. Generalized GA typically presents later in life and is less responsive to treatment. Classic GA is a self-limited disease, but lesions may persist for decades. Spontaneous resolution occurs in 50% of GA cases within 2 years; however, 40% of patients experience a recurrence.¹

PRESENTATION

Patients typically present with a complaint of a slowly enlarging red plaque or plaques on the extremities that may be pruritic; in generalized GA, they present with numerous small red papules generally distributed that may be asymptomatic to pruritic.

DIAGNOSIS

Clinical Diagnosis

Classically, GA presents with arcuate subcutaneous papules and plaques (Figure 14.5.1A). On closer examination, each annular papule or plaque is actually composed of several 1- to 2-mm pink, violaceous, or flesh-colored coalescing papules. Epidermal changes are notably absent. Lesions may be asymptomatic or pruritic.

Distribution is typically limited. The hands and arms are the most common site followed by the lower extremities. Generalized GA is rare but involves symmetric distribution of the upper and lower extremities. Facial lesions are rare in both localized and disseminated variants.

Classic GA can be diagnosed by clinical examination. However, biopsy is sometimes recommended to rule out other interstitial granulomatous diseases that may be associated with systemic symptoms (eg, interstitial granulomatous dermatitis, palisaded neutrophilic granulomatous dermatitis).

FIGURE 14.5.1 Clinical examples of granuloma annulare (GA). Classical GA annular plaques with central clearing on the dorsal feet (A) and patch subtype on the posterior lower leg (B). (Photos courtesy of Macrene Alexiades, MD, PhD.)

Histopathology

Punch biopsy is recommended over shave biopsy for adequate sampling of the dermis. Focal degeneration of elastic fibers is observed in both histologic and ultrasound examination of affected skin. In addition, histology reveals a perivascular lymphohistiocytic infiltrate, focal degeneration of collagen and elastic fibers, and increased mucin located in the upper to mid dermis.

Subtypes

Additional variants include papular GA, perforating GA, subcutaneous GA, and patch GA.

Papular GA

Papular GA is characterized by numerous small 1- to 3-mm skin-colored papules, which may be umbilicated. They may have some overlying scale crust.

Perforating GA

Perforating GA is characterized by granulomas with central umbilication or central crust through which collagen fibrils undergo transepidermal elimination.

Subcutaneous GA

Also referred to as deep GA or “pseudorheumatoid nodules,” subcutaneous GA is characterized by multiple subcutaneous nodules, typically on the lower extremities. More common in children and young adults, the inflammatory and necrobiotic component of subcutaneous GA affects the panniculus rather than the mid dermis as seen in classic GA. A small proportion of subcutaneous GA cases also have concomitant typical dermal histologic changes seen in classic GA.

Patch GA

Patch GA is an uncommon form of GA in which the lesions are oval, annular, or serpiginous red-brown patches rather than raised plaques (Figure 14.5.1B). It is usually found on the proximal extremities or trunk and may be disseminated or localized. Histology can be similar to that of interstitial GA or incomplete GA.

Differential Diagnosis

The differential of GA includes other granulomatous diseases and other annular dermatoses.

Other Granulomatous Diseases