Abstract
This case report presents a rare familial cluster of erythema nodosum (EN) secondary to streptococcal infection in a 33-year-old Iranian woman and her two children, aged 13 and 8 years. EN is a form of panniculitis characterized by tender, erythematous nodules predominantly located on the lower extremities. Although various triggers have been identified, including infections, drugs, and systemic diseases, familial cases of EN are infrequently reported. All three patients presented with painful, erythematous nodules on the pretibial aspects of their lower legs, preceded by respiratory symptoms. Laboratory investigations revealed elevated antistreptolysin O (ASO) titers, leukocytosis, and increased inflammatory markers, supporting the diagnosis of EN associated with streptococcal infection. The temporal relationship between the onset of respiratory symptoms and the development of EN in all three family members suggests a shared environmental exposure to the streptococcal pathogen. This case highlights the importance of considering familial predisposition and common environmental exposures in the etiology of EN. Furthermore, it emphasizes the value of a comprehensive clinical evaluation and targeted laboratory tests in establishing the diagnosis and identifying the underlying cause. Prompt recognition and appropriate management of EN are crucial for optimal patient outcomes and the prevention of potential complications. The familial occurrence of EN underscores the need for further research to elucidate the genetic and environmental factors contributing to the development of this rare condition and to improve our understanding of its pathogenesis and management.
Key words: Erythema nodosum, Familial, Streptococcus, Genetic, Extremities