[Erythema nodosum: Analysis of 91 hospitalized patients]

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.

To identify the main etiologies of EN among patients admitted to a medicine service of a clinical hospital.

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.

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.

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.