🔍 Search
PanniculitisMarker of systemic diseaseICD-10 L52

Erythema nodosum

EN · septal panniculitis · erythema contusiformis (chronic)

Erythema nodosum is the commonest septal panniculitis, presenting as tender erythematous subcutaneous nodules on the pretibial region. It is a non-specific reactive process; an identifiable trigger is found in roughly half of cases, the remainder being idiopathic. UK common triggers include streptococcal infection, sarcoidosis, inflammatory bowel disease, drug reactions (sulfonamides, OCP, COVID vaccines), pregnancy, tuberculosis and malignancy. A structured workup for underlying cause is essential, particularly to exclude sarcoidosis (Löfgren syndrome), TB and IBD.

CurrentLast reviewed 16 May 2026
Clinical image of Erythema nodosum
Erythema nodosum. Image sourced from DermNet New Zealand. Used under CC BY-NC-ND 4.0. No endorsement implied.

Pathogenesis

  • Type-III / IV hypersensitivity reaction with immune-complex deposition in subcutaneous venules.
  • Septal panniculitis — inflammation of fibrous septa of subcutaneous adipose tissue; no necrosis.
  • Female > male (3:1); peak 20-40 years.

Aetiology

Identifiable trigger in ~60%:

  • Infections:
    • Group A streptococcal infection (commonest UK trigger, post-pharyngitis).
    • Tuberculosis (primary or reactivated).
    • Mycoplasma pneumoniae, chlamydia, Yersinia, Salmonella, EBV, hepatitis B/C, HIV.
    • Fungal: histoplasmosis, coccidioidomycosis (US / endemic).
  • Systemic inflammatory disease:
    • Sarcoidosis — Löfgren syndrome (EN + hilar lymphadenopathy + arthralgia + fever; 70% remission within 2 years).
    • Inflammatory bowel disease (Crohn > UC).
    • Behçet disease.
  • Drugs: sulfonamides, OCP, penicillins, COVID vaccines, gold, bromides, halides.
  • Pregnancy (any trimester).
  • Malignancy: lymphoma (Hodgkin), leukaemia, internal carcinoma; rare.
  • Idiopathic (~40%).

Clinical features

  • Acute onset of 1-10 cm tender erythematous indurated nodules.
  • Predominantly pretibial; less commonly thighs, forearms, trunk.
  • Pain, warmth; do not ulcerate; bilateral.
  • Evolution through bruise-like colour changes (red → blue / green / yellow) over 1-2 weeks — "contusiform".
  • Resolution in 3-6 weeks without scarring.
  • Prodrome: malaise, fever, arthralgia (especially with Löfgren syndrome).
  • Recurrence in 1/3 of patients.

Differentials

  • Erythema induratum (Bazin) — lobular panniculitis; calf rather than shin; ulcerates; TB association.
  • Subcutaneous fat necrosis (lupus profundus, post-traumatic).
  • Lipodermatosclerosis — chronic venous; medial supramalleolar.
  • Cellulitis.
  • Cutaneous polyarteritis nodosa — livedo + nodules + ulceration.
  • α1-antitrypsin deficiency panniculitis.
  • Sweet syndrome, Wells syndrome.
  • Necrobiosis lipoidica — chronic, atrophic, yellow.
  • Cutaneous metastases.

Workup

  • Detailed history: recent infection (sore throat, GI), drug exposure, COVID vaccine timing, foreign travel, GI symptoms (IBD), ocular / respiratory symptoms (sarcoid), pregnancy.
  • Examination: chest, joints, eyes, GI / abdominal exam.
  • Bloods: FBC, CRP, ESR, ASOT, anti-DNase B, IGRA (TB), serum ACE, calcium, LFT, U&E, β-hCG.
  • Imaging: chest X-ray (sarcoid / TB / lymphoma); USS abdomen / colonoscopy if GI symptoms.
  • Microbiology: throat swab, stool culture, HIV / HepB/C if indicated.
  • Skin biopsy only if atypical / persistent / nodes-elsewhere (deep wedge to include subcutaneous fat).

Management

  • Treat underlying cause where identified — antibiotics for streptococcal, IBD therapy, withdraw drug.
  • Symptomatic:
    • Bed rest, leg elevation.
    • NSAIDs (ibuprofen, naproxen).
    • Compression stockings during ambulation.
  • Severe / refractory:
    • Potassium iodide 300-900 mg / day for 3-4 weeks.
    • Colchicine 1-2 mg / day.
    • Hydroxychloroquine.
    • Oral prednisolone 0.5 mg/kg / day taper (only after malignancy / TB excluded).
    • Dapsone, methotrexate for chronic / recurrent.
  • Resolves in 3-6 weeks in most cases.
  • Counsel about contusiform colour change without scarring.
  • Refer to specialist (rheumatology, GI, respiratory, ID) per identified trigger.

References

  1. Schwartz RA, Nervi SJ. Erythema nodosum: a sign of systemic disease. Am Fam Physician. 2007;75:695-700.
  2. Mert A et al. Erythema nodosum: an experience of 10 years. Scand J Infect Dis. 2004;36:424-427.
  3. Requena L, Yus ES. Erythema nodosum. Semin Cutan Med Surg. 2007;26:114-125.
  4. NICE CKS. Erythema nodosum. London: NICE; accessed 18 May 2026.

Spot a correction?

If any clinical statement, citation or link on this page needs updating, please email admin@skinoncology.net with the page name, the proposed correction and the supporting source.