ABSTRACT
Background: Erythema Nodosum (EN) is an acute nodular erythematous cutaneous eruption. It is presumed to be a hypersensitivity reaction and it may be idiopathic, or occur in association with diverse diseases and medications. Aim: To identify the main etiologies of EN among patients admitted to a medicine service of a clinical hospital. Material and Methods: Analysis of medical records of patients discharged with the diagnosis of EN during a ten years period. Patients were considered to have secondary EN when an underlying condition was found, and to have idiopathic EN when no such condition was found. Results: One hundred twenty nine patients were identified, but 91, aged 38 ± 14 years (86% females) had available clinical information. The etiology was idiopathic in 32% and secondary in 68% of patients. The leading etiologies were post-Streptococcal in 32%, followed by sarcoidosis in 11%, primary tuberculosis in 7%, Mycoplasma infection in 3%, Bartonella infection in 3%, Behçet’s syndrome in 2%, inflammatory bowel disease in 2%, drugs in 1% and other etiologies in 8%. Secondary cases of EN had higher levels of C Reactive Protein and leucocytes than idiopathic cases. Conclusions: The distribution of causes in our study population were similar to those reported in the literature (With smaller proportion of idiopathic), as was the man/woman (1/6) ratio, and the preponderance of cases in winter and spring. Infectious diseases were the leading causes of EN in this group of patients, and a reasonable initial approach in the hospital should include a diligent medical history and physical examination, complete blood count, ESR, titles ASO, PPD tuberculin skin test, chest X-ray or CT scan and, where deemed appropriate, specific autoimmune and infectious serology.