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).