Erythema Nodosum

Question 1

Definition

Answer 1

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

Question 2

Aetiology/Risk factors

Answer 2

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

· Infection
o Bacterial - e.g. streptococcus
o Viral - e.g. EBV
o Fungal - e.g. histoplasmosis

· Systemic Disease
o Sarcoidosis
o IBD
o Behcet’s disease

· Malignancy
o Leukaemia
o Hodgkin’s disease

· Drugs
o Sulphonamides
o Penicillin
o 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

Presenting 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 on physical examination

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 (bloods)

Answer 6

o Anti-streptolysin-O titres (check for streptococcal infection)

o FBC/CRP/ESR - check for signs of infection/inflammation

o U&Es

o Serum ACE (raised in sarcoidosis)

Question 7

Investigations

Answer 7

· Determine underlying CAUSE

· 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