Limtong P, Suchonwanit P, Chanprapaph K, et al. - Findings revealed that clinical risk factors were not related to the etiology of erythema nodosum (EN), but idiopathic EN was suggested by histopathological presence of eosinophils in focal peripheral lobular panniculitis.

• A retrospective review of 169 patients with biopsy-proven EN or septal panniculitis, who were classified as either idiopathic or secondary EN.

• Mean age at EN diagnosis was 40.6 ± 17.3 years, 62.7% had idiopathic EN, and main causes of secondary EN include tuberculosis (23.8%) and drugs (23.8%).

• Factors, in univariate logistic regression analysis, that favored secondary EN were: lesions on upper extremities, fever, clinical lymphadenopathy.

• Multivariable logistic regression analysis did not reveal factors linked with secondary EN.

• Recurrence occurred in 46.6% of cases with no detectable predictive factors.