Granuloma annulare

Meet the patient

A 24-year-old teacher notices a painless ring of skin-coloured bumps on the back of her right hand that has been slowly enlarging for two months. The ring is smooth, firm, not scaly, and not itchy. She has put antifungal cream on it twice with no change.[1]

The two questions that settle her consult are the two that settle every GA: is this fungal, or is this a granuloma? (look for scale and do a KOH) and does the extent demand a diabetes screen? (a handful of acral lesions does not; trunk involvement does). Hold those two and the rest is detail.[1]

What GA is — and the one thing that is never true

Granuloma annulare is a benign, self-limiting granulomatous dermatosis of the dermis. It is not infectious, not contagious, and not neoplastic — three negatives worth saying out loud to a worried patient. The defining histology is the palisading granuloma: a central focus of necrobiotic (degenerated) collagen bathed in mucin, ringed by histiocytes and the occasional multinucleated giant cell.[1]

The name is its own teaching. Granuloma points to the histiocytic infiltrate; annulare points to the ring shape of the common localised form. But not every GA is annular — patch-type and subcutaneous forms break the ring rule entirely, and the histology, not the shape, is the diagnosis.[2]

The classic trap: everyone reaches for antifungal cream on a GA ring because it looks annular. GA is the annular lesion with no scale. If the surface is smooth and KOH is negative, stop treating fungus.[3]

The five faces — morphology is the whole classification

GA is classified by how it looks and where, not by aetiology. Five variants sit along a spectrum of depth and extent, and the variant decides both the differential and the work-up.[3]

[1]

The discriminator line: localised disease lives on the dorsa of hands and feet and resolves; generalised disease lives on the trunk and persists. The site tells you whether to reassure or to screen.[4]

How common, who, and why it forms

GA is common, though exact numbers are fuzzy because most localised cases resolve before they are biopsied. It spans every age and ethnicity, with no strong racial skew, but the variants have different demographics worth remembering.[1]

[4]

The aetiology is unknown, but a handful of triggers lead the history. Reported precipitants — physical trauma, insect bites, sun exposure, tattoo reactions, varicella scars — produce GA at the site of injury (the Koebner phenomenon). Infections (HIV, hepatitis B and C, EBV, streptococcus, tuberculosis) and drugs (allopurinol, gold, ACE inhibitors, statins, antimalarials) appear in temporal association, almost certainly as immune-mediated reactive patterns rather than direct infection.[1]

The systemic association that actually changes practice is metabolic. Generalised GA carries a real link with diabetes mellitus, dyslipidaemia and thyroid disease, and in atypical or elderly presentations with malignancy, especially lymphoma. These are not curiosities — they are the reason the disseminated form earns a blood panel.[1][6]

Why the granuloma forms — mucin is the punchline

GA is a Th1-driven, delayed-type hypersensitivity reaction against altered dermal collagen. Histiocytes are recruited to damaged collagen and organise into the palisade; fibroblasts, stirred by the cytokine soup, lay down mucin in the centre. The single most useful fact in GA histology flows from this: mucin is present in GA and absent in its main mimics.[2]

Mucin is a mix of acid mucopolysaccharides, principally hyaluronic acid. It is the histological fingerprint that separates GA from sarcoidosis (naked granulomas, no mucin), necrobiosis lipoidica (layered horizontal granulomas, no mucin), and the rheumatoid nodule (fibrinoid necrosis, minimal mucin). When the histology is subtle, Alcian blue or colloidal iron stains the mucin blue and makes the call.[3]

Mnemonic with a scene — MUCIN: Mucin is the central hallmark of GA; Usually absent in sarcoidosis and necrobiosis lipoidica; Central necrobiotic collagen sits beside it; Interstitial pattern is the less common variant; Not fibrinoid necrosis — that is a rheumatoid nodule. Picture mucin as the blue puddle in the middle of every GA granuloma, and you have the discriminator.[2]

The differential — scale is the divider

The differential of GA turns entirely on the morphology in front of you. An annular plaque is one problem; a deep nodule in a child is another. Get the morphology right and the list writes itself.[3]

[3]

The bedside sieve for any annular lesion — five questions that separate GA from its mimics:[3]

• Scale? GA is smooth; tinea and psoriasis carry scale.
• Site? GA favours dorsal hands and feet; necrobiosis lipoidica lives on the shins.
• Symptom? GA is asymptomatic; tinea itches.
• KOH? Positive hyphae confirm tinea; negative points to GA.
• Diascopy? Apple-jelly suggests sarcoidosis, not GA.[3]

The bedside round — confirm the morphology, then decide on biopsy

Examination in suspected GA is about confirming the ring and deciding whether to biopsy. Run the focused skin check in this order: count and map the lesions (fewer than ten in an acral pattern favours localised; trunk involvement flags generalised), confirm the smooth firm papular border with central clearing, look hard for absent scale, and palpate for the deep firm nodule of subcutaneous disease.[1]

When to biopsy: atypical morphology, a deep nodule in a child (to exclude sarcoma), patch-type disease, refractory or recurrent lesions, and any presentation where sarcoidosis, necrobiosis lipoidica, or cutaneous lymphoma are credible. A punch from the active edge usually reaches the dermis and shows the palisading granuloma; add Alcian blue if the picture is subtle.[4]

When to screen for systemic disease — and when not to. A typical child or young adult with localised acral GA needs no blood tests. Screen when disease is generalised, atypical, refractory, or in an elderly patient with new-onset dissemination, and when subcutaneous GA is uncertain enough to need rheumatoid serology.[1]

The targeted panel for generalised GA: fasting glucose and HbA1c (diabetes), lipid profile (dyslipidaemia), TSH and free T4 (thyroid disease), HIV test if risk, rheumatoid factor and anti-CCP for subcutaneous nodules, and age-appropriate malignancy screening — especially a lymphoma work-up if B symptoms or lymphadenopathy appear.[4]

Management — extent decides everything

GA is benign, and most localised disease is best left alone. The treatment ladder is driven by subtype, extent, symptoms and patient preference — not by a drive to eradicate every lesion.[4]

Localised GA — observe first

Observation and reassurance are first-line, especially in children. Reserve active treatment for symptomatic, cosmetically distressing, or persistent lesions.[1]

• Potent topical corticosteroid — clobetasol propionate 0.05 percent ointment once or twice daily for 2–4 weeks then tapered; occlusion boosts penetration; watch for atrophy on the dorsal hands.[5]
• Intralesional triamcinolone acetonide 2.5–5 mg/mL into the active border (10–20 mg/mL for thicker lesions) — the most useful single move for a few stubborn lesions; risk of atrophy and hypopigmentation.[5]
• Cryotherapy, topical calcineurin inhibitors (tacrolimus 0.1 percent, pimecrolimus 1 percent — steroid-sparing on the face and in children), imiquimod, and narrowband UVB for multiple refractory lesions.[4]

Generalised GA — a stepwise climb, no certain winner

There is no single first-line systemic agent for generalised GA — the evidence is case series and the 2025 Bettolini systematic review, not trials. Climb the ladder by comorbidity and tolerance.[4]

• Hydroxychloroquine 200–400 mg orally daily (commonly 200 mg twice daily) — modulates Th1 cytokines; baseline and periodic ophthalmology after five years of cumulative use.[4]
• Dapsone 50–100 mg orally daily (start 25 mg to limit haemolysis) — CHECK G6PD first; monitor full blood count and liver function; useful when neutrophils dominate.[4]
• Isotretinoin 0.5–1 mg/kg/day and methotrexate 7.5–25 mg once weekly with folic acid — second-line; pregnancy prevention for isotretinoin, blood and liver monitoring for methotrexate.[4]
• Narrowband UVB or PUVA for widespread disease — two to three sessions weekly for weeks to months.
• Biologics (adalimumab 80 mg then 40 mg alternate weeks, infliximab, ustekinumab, secukinumab) for refractory disease — screen TB and hepatitis B first.[4]

Subcutaneous GA — reassure, do not rush to excise

Subcutaneous GA in children is self-limiting; reassurance is the treatment. Excisional biopsy is both diagnostic and therapeutic only when the lesion is painful, cosmetically unacceptable, or the diagnosis is genuinely uncertain. Recurrence is common, and surgery is not a cure.[4]

The subtypes that bite — the child's nodule

Subcutaneous GA is the variant that traps candidates. A firm, painless, deep nodule on the scalp or pretibial area of a two- to five-year-old looks exactly like a rheumatoid nodule and alarms parents about juvenile arthritis. The discriminator is decisive: RF and anti-CCP are negative, there is no arthritis, and the lesion resolves on its own. Soft tissue sarcoma is the other fear — biopsy settles it when imaging or the clinical course is atypical.[2]

Perforating GA announces itself with a central crust or keratotic plug — necrobiotic collagen extruded through the epidermis. The crusting is easily misread as infection; the histology shows trans-epidermal elimination. Treat with topical steroid or cryotherapy.[1]

Generalised GA in an older adult is a metabolic signal, not just a rash. Screen diabetes, lipids, thyroid and HIV, and hold a low threshold to consider lymphoma if the course is refractory or B symptoms appear. Optimising glycaemic control matters for the patient's health, though it does not reliably clear the skin.[1]

How patients come to harm — the preventable list

GA itself is benign and never kills, so the preventable harms are all errors of over- and under-doing:[4]

• Treating GA as tinea for months because no one did a KOH — the recurring primary-care error.
• Over-treating localised GA with systemic agents that expose a self-limiting disease to toxicity.
• Missing generalised GA as the clue to undiagnosed diabetes in an older adult.
• Labelling a child's subcutaneous nodule as a rheumatoid nodule or sarcoma without negative RF and biopsy.
• Accepting "GA" on an atypical, refractory lesion that is in fact sarcoidosis, necrobiosis lipoidica, or cutaneous lymphoma.[4]

Prognosis and disposition

Localised GA has an excellent prognosis — 50 to 75 percent resolve spontaneously within months to a few years, though recurrence at the same or a new site affects roughly 40 percent. Generalised GA is more chronic and may persist for years. Subcutaneous GA in children resolves on its own. Perforating GA may scar or leave dyspigmentation.[4]

Most localised GA is managed in primary care or general dermatology. Refer when the diagnosis is uncertain, disease is generalised or refractory, a subcutaneous or perforating variant is suspected, or systemic therapy is on the table.[1]

Evidence and regional deltas

There are no large randomised trials in GA; management rests on case series, small cohorts, expert consensus, and the 2025 Bettolini systematic review of generalised GA. The diabetes association is debated — strongest for generalised disease, weak for localised — so screen the disseminated patient but do not label every GA patient diabetic.[1]

Regional deltas: the framework (observe localised, escalate generalised) is globally consistent, but cost and access shape the systemic choice. In India and resource-limited settings, topical and intralesional steroids, dapsone and hydroxychloroquine are the accessible backbone, phototherapy sits in larger centres, and biologics are reserved for the few. In TB-endemic regions, biopsy and staining matter more, because cutaneous tuberculosis and fungal infections join the differential of any granulomatous annular lesion.[4]

The mantra, and the mnemonic

[2]

The mantra: smooth ring, no scale, KOH negative — and if it is everywhere, screen for sugar.[1]

Ward-round test — three stems, thirty seconds each

Stem 1 — the ring on the hand (answer)

A 24-year-old with a slowly enlarging, painless, skin-coloured ring of firm papules on the dorsum of her right hand. No scale, no itch, two failed courses of antifungal cream. What is it, and what is the single bedside test that settles fungus versus granuloma? Model: This is localised granuloma annulare — the smooth, non-scaly, firm annular plaque on the dorsum of the hand. The discriminator from tinea corporis is the absent scale and a negative KOH preparation. Reassure: localised GA is self-limiting. If symptomatic or cosmetically distressing, intralesional triamcinolone 2.5–5 mg/mL into the active border is the most useful single treatment.[3]

Stem 2 — the child with the deep nodule (answer)

A four-year-old boy has a firm, painless lump on his pretibial area. His mother is terrified it is cancer. RF is negative, there is no arthritis, and ultrasound shows a superficial granulomatous nodule. What is the diagnosis and the plan? Model: This is subcutaneous granuloma annulare (pseudorheumatoid nodule) — the commonest deep nodule of children aged 2–5 years. The negative rheumatoid factor and absent arthritis separate it from a rheumatoid nodule; the benign histology separates it from sarcoma. Reassure the family — it is self-limiting. Excise only if painful, cosmetically unacceptable, or diagnostically uncertain; recurrence is common.[2]

Stem 3 — the disseminated rash in the older adult (answer)

A 62-year-old man develops hundreds of skin-coloured and pink papules across his trunk and extremities over three months, biopsy-confirmed as granuloma annulare. What must you do next, and why? Model: Generalised granuloma annulare in an older adult is a metabolic signal — screen for diabetes mellitus (fasting glucose, HbA1c), dyslipidaemia (lipid profile), thyroid disease (TSH, free T4), and HIV, and hold a low threshold to consider occult malignancy, especially lymphoma, if B symptoms or lymphadenopathy appear. Optimising glycaemic and lipid control helps the patient even if it does not reliably clear the skin. Treatment of the GA itself climbs the systemic ladder: hydroxychloroquine, dapsone, phototherapy, then biologics for refractory disease.[4]

References

1. [1]Joshi TP, Duvic M. Granuloma Annulare: An Updated Review of Epidemiology, Pathogenesis, and Treatment Options Am J Clin Dermatol, 2022.PMID 34495491
2. [2]Terziroli Beretta-Piccoli B, Mainetti C, Peeters MA, et al. Cutaneous Granulomatosis: a Comprehensive Review Clin Rev Allergy Immunol, 2018.PMID 29352388
3. [3]Trayes KP, Savage K, Studdiford JS. Annular Lesions: Diagnosis and Treatment Am Fam Physician, 2018.PMID 30216021
4. [4]Bettolini L, Maione V, Carugno A, et al. Management Strategies for Generalised Granuloma Annulare: A Systematic Review of Current and Emerging Therapies Australas J Dermatol, 2025.PMID 40586485
5. [5]Keimig EL. Granuloma Annulare Dermatol Clin, 2015.PMID 26143416
6. [6]Lima AL, Illing T, Schliemann S, et al. Cutaneous Manifestations of Diabetes Mellitus: A Review Am J Clin Dermatol, 2017.PMID 28374407