title: Erythema nodosum versus nodular vasculitis.
abstract: BACKGROUND
  Erythema nodosum (EN) is usually considered to be a septal panniculitis, and nodular vasculitis (NV) a lobular panniculitis. We tested the usefulness of this histologic classification in clarifying a frequent clinical dilemma: EN versus NV.
  
  
  METHODS
  Over 3 years 109 patients with panniculitis were included in this study. After a history and a physical examination, a clinical diagnosis was made according to well-established criteria.
  
  
  RESULTS
  From the study of 88 patients, we concluded that in the clinically typical cases, the clinico-pathologic agreement was 93% and 94% for EN and NV respectively, whereas it diminished to 79%, 72%, and 67% in the cases clinically diagnosed as EN migrans, atypical EN, and atypical NV, respectively. Moreover, septal and lobular panniculitis were always two clear-cut, different, opposite patterns of hypodermal inflammation to these conditions.
  
  
  CONCLUSIONS
  In the absence of a known pathogenetic mechanism, the histopathology remains the most objective discriminating marker between EN and NV, mainly in the clinically atypical and doubtful cases.
authors.affiliation: Department of Dermatology, Hospital Universitario San Carlos, Facultad de Medicina, Universidad Complutense, Madrid, Spain.
authors.forename: M D
authors.initials: MD
authors.lastname: Sanz Vico
authors.forename: V
authors.initials: V
authors.lastname: De Diego
authors.forename: E
authors.initials: E
authors.lastname: Sánchez Yus
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002648:Child; D002908:Chronic Disease; D003937:Diagnosis, Differential; D004893:Erythema Nodosum / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015434:Panniculitis / Q000473:pathology*; D012737:Sex Factors; D014657:Vasculitis / Q000473:pathology*