Erythema Nodosum and Associated Pathophysiological Mechanisms
Summary
Erythema nodosum (EN) is the most common form of panniculitis, presenting as tender, erythematous nodules classically distributed over the anterior lower legs. It represents a septal panniculitis without primary vasculitis and is regarded as a cutaneous manifestation of a systemic delayed-type (Type IV) hypersensitivity reaction. Predisposing factors include infections (notably streptococcal pharyngitis and Mycobacterium tuberculosis), sarcoidosis, inflammatory bowel disease, medications (for example hormonal therapies and, more rarely, vaccines) and pregnancy. Genetic susceptibility appears to modulate individual risk, while environmental triggers initiate an immune cascade: antigen exposure leads to T-cell activation within the dermal and subcutaneous tissue, release of pro-inflammatory cytokines (such as tumour necrosis factor-α and interleukin-6) and recruitment of macrophages, resulting in septal oedema and nodule formation. Histopathology reveals widened septa with lymphohistiocytic infiltrates, occasional multinucleate giant cells and variable lipomembranous fat necrosis. Clinically, EN follows an acute course of 2–6 weeks with spontaneous resolution in most cases, although recurrences are frequent where the underlying stimulus persists. A systematic diagnostic approach combines clinical assessment, inflammatory markers and targeted investigations to identify and manage the precipitating cause, underscoring its global relevance in both resource-rich and resource-limited settings.
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Erythema Nodosum and Associated Pathophysiological Mechanisms publication trend
The graph below shows the total number of articles in erythema nodosum and associated pathophysiological mechanisms across all publications each year (not limited to Nature Index journals).
Technical terms
Panniculitis: Inflammation of the subcutaneous fat layer, often manifesting as nodules or plaques.
Septal panniculitis: Inflammatory process predominantly within the fibrous septa separating fat lobules, with minimal lobular involvement.
Type IV hypersensitivity reaction: Delayed, T-cell mediated immune response leading to local tissue injury upon antigen recognition.
Cytokine: Small signalling protein released by immune cells to coordinate and amplify inflammatory processes.
Granuloma: Organised aggregate of macrophages and lymphocytes formed around persistent antigenic stimuli or foreign material.
References
- Erythema Nodosum in Children: A Narrative Review and a Practical Approach. Children (2022).
- A Case of Erythema Nodosum in a 20-Year-Old Female During the Postpartum Period. Cureus (2024).
- Delayed Recurrent Erythema Nodosum Following COVID-19 Vaccine: A Case Report. Cureus (2023).
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