Background Erythema nodosum (EN) is a cutaneous reaction consisting of inflammatory, tender and nodular lesions. It has been associated with a variety of disorders, especially mycobacterial and streptococcal infections, followed by other types of infections, chronic inflammations, malignancies, and exposure to certain medications.

Objectives The aim of our study was to examine the frequency and clinical features of EN, establish disease associations and identify the predictors factors for the occurrence of secondary EN.

Methods Thirty EN patients were investigated in a prospective study during the period 2008–2011. The evaluation of all patients began with a medical and family history and completed with a thorough physical examination and detailed laboratory and immunological work-up. Patients were classified as having either idiopathic EN when no such condition was found or EN secondary to other diseases if the skin nodules occurred in the context of a well-defined disease. Presentation and differences between secondary and idiopathic forms of EN were analyzed. The data were compared by the Chi squared correct by fisher exact test and student test.

Results The majority of the patients were female (28 women and 2 men). Their mean age was 39.3 years (27–59 years). In 66.6% the cause of EN was found. The foremost aetiology was post-streptococcal (45%), followed in decreasing order by a Behçet’s disease (20%), sarcoidosis (10%), inflammatory bowel diseases (IBD) (10%), pregnancy (5%), induced drug (5%) and acute leukemia (5%). All the patients were followed for a mean duration of 26 months. All the patients had bed rest and the majority was given colchicine or non-steroidal anti-inflammatory drugs. One patient was treated by oral potassium iodide solution. The patients with an underlying disease were given specific treatment. The outcomes were usually favourable. The nodosities relapsed in 60% of idiopathic EN patients but in only 1 (Behçet’s disease) of the secondary ones. Factors favouring secondary EN were as follows: prolonged fever, cough, sore throat, not relapsing EN, leukocytosis, an inflammatory syndrome and and a significant change in antistreptolysin O (ASLO) titer in 2 consecutive determinations performed in a 2-4-week interval.

Conclusions Our study revealed streptococcal pharyngitis and Behçet’s disease as the main aetiologies of EN, whereas primary tuberculosis was not found. A basic procedure including careful medical history-taking, a physical examination, 2 consecutive ASLO determinations, a tuberculin skin test, and chest radiography may be sufficient to diagnose etiology of EN.

1. García-Porrúa C, González-Gay MA, Vázquez-Caruncho M, López-Lazaro L, Lueiro M, Fernández ML et al. Erythema nodosum: etiologic and predictive factors in a defined population. Arthritis Rheum. 2000;43:584-92.

2. Mert A, Ozaras R, Tabak F, Pekmezci S, Demirkesen C, Ozturk R. Erythema nodosum: an experience of 10 years. Scand J Infect Dis. 2004; 36 :424-7.

Disclosure of Interest None Declared