🌸 Erythema Nodosum (EN) is a hypersensitivity reaction presenting with painful, indurated, shiny, red-hot nodules (1–3 cm) - classically on the shins. Included as seen with Sarcoidosis which is on the MLA🦵

ℹ️ About

Represents an immune-mediated panniculitis (inflammation of subcutaneous fat).
Often associated with systemic disease or infections.
Self-limiting but may recur.

🔬 Pathology

Type IV hypersensitivity → immune response to foreign antigens.
Causes septal panniculitis without vasculitis (key histological point).
Legs affected due to poor lymphatic drainage and hydrostatic pressure.

🦠 Causes

📌 Bacterial: Streptococcus (most common), Tuberculosis, Leprosy, Yersinia.
🦠 Viral/Other infections: EBV, Chlamydia, Histoplasmosis, Toxoplasmosis, Salmonella, Campylobacter, Rickettsia.
💊 Drugs: Sulphonamides, OCP, Penicillin, Tetracyclines, Sulphonylureas.
🧬 Systemic conditions: Sarcoidosis, Behçet’s, IBD (Crohn’s/UC), Haematological malignancy, Pregnancy.
❓ Idiopathic in many cases.

🩺 Clinical Features

Painful, red, hot nodules (1–3 cm) → typically on the shins.
Lesions evolve: red → violaceous → bruise-like fade; no ulceration/scarring.
Crops last 3–6 weeks, with new lesions appearing.
Associated systemic features: fever, malaise, arthralgia.
♀️ More common in females (young adults).

🧾 Investigations

Bloods: FBC, CRP/ESR, ASO titre, Serum ACE (for sarcoid).
Microbiology: Throat swab (strep screen).
Imaging: CXR for bihilar lymphadenopathy (sarcoid, TB).
Tuberculosis screen (Heaf or Mantoux).

💊 Management

Identify and treat underlying cause (e.g., strep, TB, IBD).
Supportive: rest, leg elevation, compression stockings.
Symptomatic: NSAIDs or potassium iodide.
Severe/refractory: Colchicine, Dapsone, Corticosteroids (caution: exclude infection first!).
Spontaneous resolution usually in 3–6 weeks, but full resolution may take up to 3–6 months.

🩺 Case 1 : Post-Streptococcal Infection

A 22-year-old woman presents with painful red nodules over both shins, fever, and sore throat 2 weeks ago. Throat swab grew group A streptococcus. Exam shows tender, raised, erythematous lesions on the anterior tibiae. Management: 💊 Treat underlying streptococcal infection (penicillin), NSAIDs for pain, bed rest, supportive care. Avoid: ❌ Ignoring possible underlying infection; avoid corticosteroids unless infection excluded.

🩺 Case 2 : Sarcoidosis

A 35-year-old woman presents with painful shin nodules, dry cough, and fatigue. CXR shows bilateral hilar lymphadenopathy. Diagnosis: sarcoidosis presenting with erythema nodosum and pulmonary involvement. Management: 🩺 NSAIDs for pain; systemic corticosteroids if significant pulmonary disease. Monitor with respiratory team. Avoid: ❌ Relying on NSAIDs alone if there is progressive sarcoidosis; avoid long-term steroids without specialist supervision.

🩺 Case 3 : Drug-Induced

A 40-year-old man develops painful nodules on his legs 3 weeks after starting sulfonamide antibiotics for a urinary tract infection. He is otherwise well with no systemic features. Management: 💊 Discontinue offending drug, symptomatic relief with NSAIDs, compression stockings if needed. Avoid: ❌ Re-challenging with the culprit drug; avoid unnecessary antibiotics in the future.

The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms.

Erythema Nodosum