Granuloma annulare
Definition & Classification
- Granuloma annulare (GA) = chronic-recurrent, granulomatous skin disease with annular plaques.
- Clinical Subtypes: localized + generalized + subcutaneous as well as perforating.
Pathogenesis
- Immunological Reaction due to misdirected immune response to various triggers:
- Comorbidities: Diabetes mellitus, thyroid autoimmunity, hyperlipidemia (especially in generalized form), HIV.
- Cellular Infiltration: T-cells + macrophages + fibroblasts infiltrate the dermis and form granulomatous lesions.
- Cytokines / Chemokines: IL-2, IL-4, IL-10, IL-12, TNF-α, IFN-γ — Th1 / Th17 + Th2 mixed pattern with fibroblast activation.
- Fibroblast activation: Production of degraded collagen + mucin in the center of the granuloma, annular growth.
Clinical Presentation
- Classic (localized): annular erythematous papules on dorsa of hands/feet + extensor surfaces.
- Generalized: > 10 lesions, often trunk + extremities, more common in adulthood, associated with DM Type 1 and hyperlipidemia.
- Subcutaneous: painless subcutaneous nodules, often on the tibia / shin in children — DD to rheumatoid nodules important (Subcutaneous nodules of childhood).
- Perforating: umbilicated papules with crusts; rare.
- Patch / patchy: flat brownish-erythematous plaques.
- Dermoscopy: non-specific, but useful for ruling out: fine dotted vessels on a dull-pink background with whitish streaks in between. What is decisive is what is missing — no pigment network (against a melanocytic lesion), no marginal scaling (against tinea corporis), no evenly distributed red dots with silvery scale (against psoriasis).
- Symptoms: mostly asymptomatic with mild pruritus.
Histology
- Characteristic: palisading granuloma with histiocytes + lymphocytes (= palisading granuloma).
- Mucin in the center of the granuloma (Alcian blue +) — important for DD to rheumatoid nodules (no mucin) and Necrobiosis lipoidica (cholesterol, less mucin).
- Immunohistochemistry: CD68+ histiocytes, CD4+/CD8+ lymphocytes, few eosinophils.
Differential diagnoses
- Tinea corporis
- Psoriasis vulgaris (plaque psoriasis)
- Nummular eczema
- Mycosis fungoides
- Granuloma faciale
- Atopic dermatitis (atopic eczema)
- Urticaria
- Cutaneous sarcoidosis
Practise Granuloma annulare in the app
Flashcards with spaced repetition, exam questions and spot-the-diagnosis on this topic – in DermaFuchs, free of charge.
In the DermaFuchs app: 7 flashcards · 7 clinical images
Open in browser Download on the App StoreMore inflammatory skin diseases
- Cheilitis granulomatosa (Miescher)
- Erythema annulare centrifugum (EAC)
- Erythema nodosum
- Graft-versus-host disease (GvHD)
- Cutaneous sarcoidosis
- Lichen planus
- Lichen sclerosus
- Lichenoid drug eruption
Note: This page is intended for medical education and does not replace diagnosis or treatment decisions in individual cases. Treatment and follow-up content is available in the app.