Clinical and biological characteristics of immunopathological disease- related erythema nodosum in children

We report a series of 22 children with idiopathic, drug unrelated erythema nodosum (EN) admitted to our Department. In 5 of them an history of streptococcal pharyngitis was referred; the remaining patients came to us with a diagnosis of 'EN of unknown origin'. Acute phase reactants, immunoglobulins, stool α1 antitrypsin, ANA, anti dsDNA antibodies and ANCA assay, chest roentgenogram, tuberculin test, and ophthalmologic assessment were performed in all patients. Etiologic diagnosis was made in 16 patients: Streptococcal pharyngitis (5 cases), chronic inflammatory bowel disease, IBD (3 cases), Behcet syndrome (2 cases), Yersinia enteritis (2 cases), infectious mononucleosis, atypical mycobacterial infection, immunodeficiency related infection, and SLE-like syndrome due to C4 deficiency (1 case each). We found oral/scrotal aphthae in 3 cases, gastrointestinal symptoms in 5 cases, arthritis in 3 cases. Acute phase reactants were positive in 16 patients without correlation to the underlying disease. Conversely, the increased α1 antitrypsin stool excretion and IgA serum concentration seemed to represent helpful indicators of IBD and Behcet syndrome, respectively. Proinflammatory cytokine pattern showed increased IL6 serum concentrations both in infectious and in non infectious disease-related EN, whereas a minor involvement of TNF was found in these patients.