Erythema nodosum
D E FI N I T ION
Panniculitis (inflammation of the subcutaneous fat tissue) presenting as red
or violet subcutaneous nodules.
AE T IOLOGY
Delayed hypersensitivity reaction to antigens associated with various infectious
agents, drugs, and other diseases.
Infection: Bacterial (Streptococcus, TB, Yersinia, rickettsia, Chlamydia, leprosy), viral (EBV),
fungal (histoplasmosis, blastomycosis, coccidioidomycosis), protozoal (toxoplasmosis).
Systemic disease: Sarcoidosis, IBD, Beh¸cet’s disease.
Malignancy: Leukaemia, Hodgkin’s disease.
Drugs: Sulphonamides, penicillin, oral contraceptive pills.
Pregnancy.
25 % of cases have no underlying cause identified.
E P IDEMIOLOGY
Usually affects young adults. , : < 3: 1.
H ISTORY
Tender red or violet nodules develop bilaterally on the shins and occasionally
on the thighs and forearms. Fatigue, fever, anorexia, weight loss and arthralgia are often
also present.
Symptoms of the underlying aetiology.
EXAMINA T I ON
Crops of red or violet dome-shaped nodules usually present on both shins
(occasionally involving thighs or forearms) which are tender to palpation.
Low-grade pyrexia. Joints may be tender and painful on movement.
Signs of the underlying aetiology.
INVE S T I G A T IONS
To determine the underlying aetiology.
Blood: Anti-streptolysin-O titre at diagnosis and 2–4 weeks later to assess for antecedent
streptococcal infection. FBC, U&Es, CRP, ESR, LFTs, serum ACE (" in sarcoidosis).
Throat swab and culture.
Mantoux/Heaf skin testing: For TB.
CXR: To look for hilar adenopathy or other evidence of pulmonary sarcoidosis, TB and fungal
infections.
MANAGEMENT
Treat the cause. In most cases, manage conservatively.
NSAIDs or potassium iodide may be given for relief of the discomfort associated with the rash.
Persistent cases may require corticosteroids, colchicine, azathioprine or dapsone. When
considering corticosteroids, clinicians should assess the possibility of masking an underlying
malignant, inflammatory, or infectious condition.
COM P L IC A T I ONS
None. Complications of the underlying cause.
PROGNOSIS
The majority of cases resolve over 3–6 weeks leaving bruise marks.
Occasionally, nodules may persist or recur over several months, but they never ulcerate.
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