Erythema nodosum

Question 1

Define

Answer 1

Panniculitis (inflammation of the subcutaneous fat tissue) presenting as red or violet subcutaneous nodules

Aetiology → Delayed hypersensitivity reaction to antigens associated with various infectious agents, drugs, and other diseases

•Often a dermatological manifestation of infectious, or other, disease

Question 2

Causes

Answer 2

Delayed hypersensitivity reaction to antigens associated with various infectious agents, drugs and diseases

Infection

• Bacterial - e.g. streptococcus
• Viral - e.g. EBV
• Fungal - e.g. histoplasmosis

Systemic Disease

• Sarcoidosis
• IBD
• Behcet’s disease

Malignancy

• Leukaemia
• Hodgkin’s disease

Drugs

• Sulphonamides
• Penicillin
• Oral contraceptive pills

Pregnancy

• 25% of cases have no identifiable cause

Question 3

Epidemiology

Answer 3

Usually affects YOUNG ADULTS

THREE times more common in FEMALES

Question 4

Symptoms

Answer 4

Tender red or violet nodules bilaterally on both shins

Occasionally on thighs or forearms

Fatigue

Fever

Anorexia

Weight loss

Arthralgia

Symptoms of underlying CAUSE

Question 5

Signs

Answer 5

Crops of red or violet dome-shaped nodules usually present on both shins

Occasionally appear on the thighs and forearms

Nodules are tender to palpation

Low-grade pyrexia

Joints may be tender and painful on movement

Signs of underlying CAUSE

Question 6

Investigations

Answer 6

Determine underlying CAUSE

Bloods

• Anti-streptolysin-O titres (check for streptococcal infection)
• FBC/CRP/ESR - check for signs of infection/inflammation
• U&Es
• Serum ACE (raised in sarcoidosis)

Throat swab and cultures

Mantoux/Head skin testing - for TB

CXR - check for bilateral hilar lymphadenopathy or other evidence of TB, sarcoidosis or fungal infections