Investigations
Investigation should be directed at finding an underlying cause:
- careful history - especially attention to drugs
- complete blood count with differential – ESR and CRP
- evaluation for streptococcal infection (e.g., throat culture for group A streptococci, anti-streptolysin O titre, and polymerase chain reaction assay)
- consider possible sarcoidosis or tuberculosis
- chest X-ray, purified protein derivative test
- viral titres may be indicated:
- viral causes of erythema nodosum include:
- herpes simplex virus, Epstein-Barr virus, hepatitis B and C viruses, human immunodeficiency virus
- viral causes of erythema nodosum include:
- stool culture may be indicated in some patients
- stool culture and evaluation for ova and parasites in patients with diarrhoea or gastrointestinal symptoms
- consider evaluation for inflammatory bowel disease
- excisional biopsy – if clinical diagnosis is in doubt
- key histologic findings are septal panniculitis, actinic (Miescher's) radial granulomas, lymphocytic infiltrate with neutrophils, absence of vasculitis, and no organisms
Reference:
- Perez-Garza D et al. Erythema Nodosum: A Practical Approach and Diagnostic Algorithm. Am J Clin Dermatol. 2021 May;22(3):367-378
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