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Erythema nodosum is a type of panniculitis (inammation of the subcutaneous fat) characterised by painful shiny red lumps usually affecting the shins, and less commonly the thighs and forearms. The red lumps later regress, becoming purple and then fading through the colour changes of a bruise over a period of about 3 – 6 weeks. It occurs more commonly in women, and in people aged 20 – 45 years. Most people with erythema nodosum are in good health but it is often associated with a recent infection or illness. Diagnosis is usually made clinically, although a skin biopsy is often performed. Erythema nodosum is treated symptomatically with NSAIDs, supportive bandages and bed rest.
Common causes include:
- Throat infections (typically streptococcal infection)
- Other bacterial infections e.g. Mycoplasma pneumoniae, Salmonella spp.
- Pregnancy or the oral contraceptive pill
- Other drugs e.g. sulphonamides, salicylates, gold
- Inflammatory bowel disease