title: Erythema nodosum: etiologic and predictive factors in a defined population.
abstract: 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 hospital between 1988 and 1997. Patients were classified as having either idiopathic 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 event in close temporal proximity to the onset of EN.
  
  
  RESULTS
  One hundred six patients (82 women) were diagnosed as having biopsy-proven EN. At the time of diagnosis, no precipitating events or underlying diseases were identified in 36.8% of patients. Sarcoidosis and nonstreptococcal upper respiratory tract infections (URI) were the most common conditions associated with secondary EN. Only 1 of 35 patients with an initial diagnosis of idiopathic EN and a followup of at least 1 year was finally diagnosed as having secondary EN. The best predictive model of secondary EN included an abnormal results on a chest radiograph, a previous history of nonstreptococcal URI, and a significant change in antistreptolysin O (ASO) titer in 2 consecutive determinations performed in a 2-4-week interval. Also, the presence of peripheral synovitis, a positive tuberculin skin test, and a history of diarrhea suggested the presence of secondary EN. This model showed high sensitivity and specificity.
  
  
  CONCLUSIONS
  Idiopathic EN is common. A basic procedure including careful medical history-taking, a physical examination for peripheral synovitis, 2 consecutive ASO determinations, a tuberculin skin test, and chest radiography may be sufficient to diagnose EN.
authors.affiliation: Hospital Xeral-Calde, Lugo, Spain.
authors.forename: C
authors.initials: C
authors.lastname: García-Porrúa
authors.forename: M A
authors.initials: MA
authors.lastname: González-Gay
authors.forename: M
authors.initials: M
authors.lastname: Vázquez-Caruncho
authors.forename: L
authors.initials: L
authors.lastname: López-Lazaro
authors.forename: M
authors.initials: M
authors.lastname: Lueiro
authors.forename: M L
authors.initials: ML
authors.lastname: Fernández
authors.forename: J
authors.initials: J
authors.lastname: Alvarez-Ferreira
authors.forename: R M
authors.initials: RM
authors.lastname: Pujol
mesh_terms: D001706:Biopsy; D004893:Erythema Nodosum / Q000453:epidemiology / Q000209:etiology / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012507:Sarcoidosis / Q000150:complications; D012621:Seasons; D013290:Streptococcal Infections / Q000150:complications; D016896:Treatment Outcome; D014376:Tuberculosis