Erythema Nodosum

Synonyms

Subacute nodular migratory panniculitis.

Epidemiology

2.4/1000 population/year, mostly Spring/Autumn (due to streptococcal infections). F:M = 3-6 : 1. Especially children and adults (20 - 40 years).

Definition

Tissue-reaction pattern with many causes, characterised by painful subcutaneous nodules on the shins, most commonly in women.

Aetiology & Pathogenesis

Specific common causes include:

Streptococcal infections
Hepatitis B
Sarcoidosis
Bowel infections (e.g. Yersinia)
Medications (e.g. penicillins, sulphonamides, oral contraceptives)
Crohn’s disease
Tuberculosis
Other causes such as cat scratch disease and ornithosis.

Signs & Symptoms

Often prodrome with malaise, fever, joint pain. Then tender, poorly defined subcutaneous erythematous nodules appear, which are warm to the touch. Over time, colour changes from bright red to dark red to yellow-brownish and finally light grey.

Localisation

Shins (occasionally thighs, buttocks or arms).

Classification

None.

Laboratory & other workups

Blood tests with several serologic markers (rheumatism, streptococci, tuberculosis, yersiniosis, angioconverting enzyme, pancreatic enzymes, antinuclear antibodies), stool culture and radiographic studies may be considered to exclude some of the known causes. Investigation is dictated by the patient’s history and examination findings.

Dermatopathology

Early phase: inflammatory infiltrate of neutrophils in the subcutaneous fat septae, oedema, macrophages and foam cells.

Later phase: granulomatous reaction and finally fibrous septae with scarring of fat tissue. It is in general a septal panniculitis.

Course

EN usually heals spontaneously without scarring within 3-6 weeks, however, after longstanding or relapsing lesions, there may be scarring.

Complications

Depends on the underlying cause. There are longstanding and migrating subtypes of EN.

Diagnosis

Clinical feature. Occasionally biopsy may be required. A careful search for the underlying disease is needed. Despite investigations, in 25-50% of cases no cause is identified.

Differential diagnosis

Erythema nodosum leprosum; erysipelas; Urticaria.

Prevention & Therapy

Depends on underlying cause. The underlying disease(s) should be treated. Systemic NSAIDs may be helpful. If the clinical symptoms are severe, short-term systemic corticosteroids may be given. Supportive measures: bed rest, heparinoid creams, and compression stockings.

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