title: Marked papillary dermal edema--an unreliable discriminator between polymorphous light eruption and lupus erythematosus or dermatomyositis.
abstract: BACKGROUND
  The clinical differential diagnosis of photo-distributed papules and plaques includes polymorphous light eruption (PMLE) and lupus erythematosus (LE). These entities share many histopathological features. However, in most contemporary textbooks, a broad band of papillary dermal edema is reported to be characteristic of PMLE and not seen in LE. Nonetheless, older reports describe papillary dermal edema in LE, including acute cutaneous LE (ACLE) in patients with systemic LE (SLE) and early lesions of discoid lupus erythematosus (DLE). Older reports also describe papillary dermal edema in microscopic sections of dermatomyositis (DM).
  
  
  METHODS
  Retrospective review.
  
  
  RESULTS
  Nine cases of LE (including two patients with acute lesions of SLE, six with DLE and one unclassifiable) and three cases of DM were identified in which sections showed striking papillary dermal edema. Attributes of chronicity, such as epidermal atrophy, follicular plugging and basement membrane thickening, were present concurrently in many sections.
  
  
  CONCLUSIONS
  Marked papillary dermal edema does not reliably distinguish PMLE from LE as it can be seen in ACLE, early and late lesions of DLE and DM. This phenomenon has been underemphasized in recent reports and textbooks. Furthermore, papillary dermal edema in chronic lesions of DLE has not been previously reported.
authors.affiliation: Department of Pathology, University of California, San Francisco, San Francisco, CA 94115, USA. pincusl@derm.ucsf.edu
authors.forename: Laura B
authors.initials: LB
authors.lastname: Pincus
authors.forename: Philip E
authors.initials: PE
authors.lastname: LeBoit
authors.forename: Deborah S
authors.initials: DS
authors.lastname: Goddard
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Cho
authors.forename: Timothy H
authors.initials: TH
authors.lastname: McCalmont
mesh_terms: D000328:Adult; D000368:Aged; D003882:Dermatomyositis / Q000473:pathology*; D003937:Diagnosis, Differential; D004487:Edema / Q000473:pathology*; D005260:Female; D006801:Humans; D008178:Lupus Erythematosus, Cutaneous / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D010787:Photosensitivity Disorders / Q000473:pathology*; D012867:Skin / Q000473:pathology*