Erythema nodosum - Etiologic and predictive factors in a defined population

Objective. To examine the frequency and features of erythema nodosum (EN), establish disease associations, and identify the optimal set of predictors for the occurrence of secondary EN. Methods. We performed a retrospective study of an unselected population of patients 14 years and older with biopsy-proven EN diagnosed at a referral h ospital between 1988 and 1997, Patients were classified as having either id iopathic EN or EN secondary to other diseases if the skin nodules occurred in the context of a well-defined disease, or if there was a precipitating e vent in close temporal proximity to the onset of EN. Results. One hundred six patients (82 women) were diagnosed as having biops y-proven EN, At the time of diagnosis, no precipitating events or underlyin g diseases were identified in 36.8% of patients, Sarcoidosis and nonstrepto coccal upper respiratory tract infections (URI) were the moat Common condit ions associated with secondary EN, Only 1 of 35 patients with an initial di agnosis of idiopathic EN and a followup of at least 1 year was finally diag nosed as having secondary EN, The best predictive model of secondary EN inc luded an abnormal results on a chest radiograph, a previous history of nons treptococcal URI, and a significant change in antistreptolysin O (ASO) tite r in 2 consecutive determinations performed in a 2-4-week interval. Also, t he presence of peripheral synovitis, a positive tuberculin skin test, and a history of diarrhea suggested the presence of secondary EN. This model sho wed high sensitivity and specificity. Conclusion, Idiopathic EN is common. A basic procedure including careful me dical history-taking, a physical examination for peripheral synovitis, 2 co nsecutive ASO determinations, a tuberculin skin test, and chest radiography may be sufficient to diagnose EN.