Causes of Erythema Nodosum
The causes of erythema nodosum are varied, and in many cases, no single cause is ever found. However, erythema nodosum is often a reaction to infection, inflammation, or medication. Identifying the cause helps doctors decide whether further treatment or investigation is necessary.
Infections
Infectious causes are among the most common, particularly:
Streptococcal throat infections – Often seen in children and young adults
Tuberculosis (TB) – A major cause in regions like South Africa, especially in rural or high-prevalence areas
HIV and associated infections – May trigger inflammatory reactions
Fungal infections – Such as histoplasmosis or coccidioidomycosis in some regions
Yersinia enterocolitica – A bacterial gut infection sometimes linked to erythema nodosum
Inflammatory and Autoimmune Conditions
Several chronic diseases can trigger the condition:
Sarcoidosis – A common cause in adults, especially when combined with symptoms like cough and swollen lymph nodes
Inflammatory bowel disease – Both Crohn’s disease and ulcerative colitis are linked
Behçet’s disease – A rare condition that may present with ulcers, joint pain, and skin lesions
Medications
Some medications can provoke a hypersensitive reaction:
Sulphonamides
Oral contraceptives
Penicillins
Non-steroidal anti-inflammatory drugs (NSAIDs)
Drug-related erythema nodosum often resolves once the medication is stopped.
Pregnancy
Hormonal changes during pregnancy may also trigger episodes of erythema nodosum, especially in the first trimester.
Causes of Erythema Nodosum In South Africa
In South Africa, TB is a leading cause. Erythema nodosum may be the first visible sign, especially in patients who have not yet shown respiratory symptoms. HIV-positive individuals are also more prone to skin-related inflammatory reactions.
Doctors in South Africa should consider TB screening and HIV testing in patients presenting with unexplained erythema nodosum.
Understanding the causes of erythema nodosum helps guide tests, treatment, and decisions about whether to investigate for underlying infections or autoimmune disorders.
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