Granuloma Annulare

Granuloma annulare (GA) is a benign, self-limiting granulomatous dermatosis characterised by annular plaques of dermal papules.

• Common in children and young adults; women more than men. Localised GA most common (75%), generalised (over 10 lesions) in older adults.
• Associations: diabetes mellitus, dyslipidaemia, thyroid disease, and occasionally malignancy, HIV, or hepatitis C; generalised GA has stronger links to diabetes and lipid disorders.
• Triggers: trauma, insect bites, UV exposure, vaccination, and medications (TNF inhibitors, allopurinol, amlodipine).
• Localised GA resolves spontaneously in about 50% within 2 years, with recurrences in 40%.

• Annular or arcuate plaques of flesh coloured, pink, or violaceous firm papules with a central clearing, usually asymptomatic; occasional mild itch.
• Sites: dorsal hands, fingers, feet, elbows, knees, and ankles.
• Variants: generalised, subcutaneous (children, nodules on legs, scalp, hands), perforating (umbilicated papules with crust), patch and arcuate dermal erythema.
• Lesions heal without scarring.

• Clinical diagnosis; dermoscopy may show orange yellow structureless areas.
• Biopsy if atypical: interstitial or palisading granulomas around degenerated collagen with increased mucin (colloidal iron stain).
• Screen for diabetes and lipid disorders in generalised disease; consider TSH and ANA.
• Exclude tinea corporis (KOH), sarcoidosis, necrobiosis lipoidica, erythema annulare centrifugum, lichen planus, and rheumatoid nodules (for subcutaneous GA).

• Reassure about self-resolution; no treatment needed for asymptomatic disease.
• Localised disease: clobetasol 0.05% ointment daily for 4 to 6 weeks, or intralesional triamcinolone acetonide 2.5 to 5 mg/mL every 4 weeks (up to 3 sessions), tacrolimus 0.1% ointment, cryotherapy (liquid nitrogen 10 to 15 seconds), and pulsed dye laser.
• Generalised or persistent disease: narrow band UVB or PUVA, hydroxychloroquine 200 mg twice daily, isotretinoin 0.5 mg/kg, dapsone 100 mg, doxycycline 100 mg twice daily, methotrexate 10 to 15 mg weekly, adalimumab 40 mg every 2 weeks or infliximab, and JAK inhibitors (tofacitinib, baricitinib).
• Treat comorbid diabetes, hyperlipidaemia, and withdraw implicated drugs.
• Subcutaneous GA in children usually regresses without treatment.