What is Granuloma Annulare?
Granuloma annulare (GA) is a benign, chronic inflammatory skin condition that presents as annular (ring-shaped) groups of skin-colored to erythematous papules without epidermal scaling, most commonly on the dorsal hands and feet. 1, 2
Clinical Presentation
- Localized GA (most common form): Grouped papules forming enlarging annular plaques, typically on lateral or dorsal surfaces of hands and feet 1, 2
- Generalized/disseminated GA: Widespread papular or annular lesions across trunk and extremities 1, 3
- Subcutaneous GA: Deep dermal or subcutaneous nodules, more common in children 1
- Perforating GA: Lesions with central umbilication and discharge of necrotic material 1
- Patch GA: Erythematous patches without prominent papules 3
The lesions are characteristically non-scaly (distinguishing them from tinea), asymptomatic, and have a flesh-colored to erythematous appearance. 2, 4
Pathophysiology and Etiology
The exact cause remains unknown, but GA has been associated with multiple triggers and conditions 1, 3:
- Trauma, insect bites, sun exposure 5
- Viral infections: Hepatitis B/C, HIV, Epstein-Barr virus, herpes zoster 5
- Systemic associations (controversial and not definitively proven): diabetes mellitus, thyroid disease, dyslipidemia, malignancy 5, 1, 3
Important caveat: While diabetes mellitus is frequently mentioned in association with GA, the relationship remains unclear and unproven. However, screening for diabetes may be warranted when GA presents, as cases have been reported where GA preceded diabetes diagnosis. 5
Diagnosis
Diagnosis relies on clinicopathological correlation with skin biopsy confirmation. 1
Histopathology
- Palisading granulomas surrounding degenerated collagen in the dermis 5, 1
- Mucin deposition 1
- Lymphohistiocytic infiltrate 1
Differential Diagnosis
GA can mimic several conditions and must be distinguished from 6, 4:
- Tinea corporis/cruris (but GA lacks scale and fungal elements)
- Necrobiosis lipoidica 6
- Pyoderma gangrenosum 6
- Sarcoidosis
- Annular lichen planus
Clinical pitfall: GA can present in atypical locations including the groin (mimicking tinea cruris), neck, and other sites beyond the classic dorsal hand/foot distribution. 5, 4 Always consider biopsy when annular lesions fail to respond to antifungal therapy.
Natural History and Prognosis
- Localized GA: Generally self-limited, resolving spontaneously within 1-2 years without treatment 1, 2
- Generalized GA: More chronic and recalcitrant, less likely to spontaneously resolve 3, 2
- Relapses occur frequently even after apparent resolution 5, 1
Treatment Approach
For Localized Disease
Mid to high potency topical corticosteroid ointment applied twice daily under occlusion is first-line treatment. 7, 8
- Intralesional triamcinolone acetonide (5-10 mg/cc) for persistent lesions that fail topical therapy 7, 8
- Alternative options: Topical tacrolimus, pimecrolimus, or vitamin D analogs combined with topical steroids for refractory cases 7, 8
- Cryotherapy with liquid nitrogen can be considered 2
For Generalized/Disseminated Disease
Narrowband UVB (TL-01) phototherapy is the recommended first-line treatment due to its superior long-term safety profile. 7, 8
- Systemic therapies for refractory cases include methotrexate, dapsone, isotretinoin, antimalarials, or fumaric acid esters 7, 1, 2
- Photodynamic therapy achieves 52% complete response but is impractical for widespread disease 7
Important Treatment Considerations
- No treatment may be appropriate for asymptomatic localized disease given its self-limited nature 2
- Over 30 different treatments have been described, but evidence is limited to case reports and small series—no gold standard exists 1, 3
- Regular follow-up to assess treatment response is necessary 7, 8
Treatment pitfall: Because generalized GA is chronic and recalcitrant, manage patient expectations regarding treatment duration and potential for recurrence. Systemic therapies require consideration of baseline laboratory values, comorbidities, drug interactions, and adverse effect profiles. 1