Introduction
Erythema nodosum (EN) is a form of panniculitis, marked by inflammation of subcutaneous fat tissue (1). Clinically, it presents as tender, erythematous nodules, predominantly located on the anterior aspects of the lower extremities. EN frequently coexists with various systemic diseases, infections, and medication reactions, and less commonly, it has a genetic predisposition (2). Familial (EN) denotes a subset of this condition, where a significant hereditary component is evident, implying a substantial role of genetic factors in its pathogenesis (3).
EN primarily affects young adults, with a higher incidence observed in females. The precise prevalence of familial cases remains undocumented due to their rarity (4). Nonetheless, it is imperative to consider a family history in the diagnostic evaluation and management of recurrent or chronic EN cases (5).
The etiology of EN is complex and not fully understood, though it is recognized as a hypersensitivity reaction to various antigens. These antigens can be exogenous, including bacterial, viral, or fungal infections, or endogenous, related to systemic conditions such as sarcoidosis, inflammatory bowel disease, and malignancies. In familial cases, a genetic predisposition is suggested, although specific genetic markers have not been conclusively identified (1).
The clinical hallmark of EN is the acute onset of painful, erythematous nodules, ranging from 1 to 5 cm in diameter (6). These nodules often develop a bruise-like appearance as they resolve. They are most located on the shins but can appear on other areas of the body. Associated systemic symptoms include fever, malaise, and arthralgia. Diagnosis of EN is primarily clinical, based on the distinctive appearance and distribution of the nodules (7).
Management of EN focuses on treating the underlying cause if identified. General supportive measures include bed rest, leg elevation, and the use of nonsteroidal anti-inflammatory drugs (NSAIDs) for pain and inflammation. In more severe cases, potassium iodide and corticosteroids may be considered (8).
The prognosis for EN is generally favorable, with most lesions resolving spontaneously within 3 to 6 weeks. However, chronic or recurrent EN, especially in familial cases, may necessitate ongoing management and monitoring for potential underlying systemic diseases (2).