title: The inflammatory response in drug-induced acute urticaria: ultrastructural study of the dermal microvascular unit.
abstract: BACKGROUND
  Drug exposure is one of the main aetiologies of urticaria and represents the second most common cause in acute urticarias. Studies involving the ultrastructural aspects of urticaria are relatively rare in the literature. Most of the articles published report on skin biopsies of experimentally induced urticaria, and acute urticaria has been studied even less from a morphological point of view.
  
  
  OBJECTIVE
  The aims of this study were to observe ultrastructural cell characteristics in five patients with drug-induced acute urticaria and possible aspects of the inflammatory skin response.
  
  
  METHODS
  Clinical manifestations, light microscopy and transmission electron microscopy were evaluated.
  
  
  RESULTS
  With light microscopy, a mild perivascular lymphocyte-monocyte infiltrate was observed with few neutrophils and dermal oedema in skin biopsies of five patients. With electron microscopy, a mild vascular dilatation was observed, with platelets in the lumen and several lymphocytes and dendritic cells close to the superficial dermal vessels. Some mast cells appeared normal, whereas others were granule-depleted. In some areas, mast cells, lymphocytes and satellite dendritic cells were closely associated, as well as some macrophages. A significant number of plasma cells, eosinophils and polymorphonuclear neutrophils were not observed; however, the presence of lymphocytes and macrophages was significant. The epidermis and the dermal-epidermal junction were preserved, except for a discrete oedema in keratinocytes.
  
  
  CONCLUSIONS
  The ultrastructural aspect of drug-induced acute urticaria is similar to that observed in urticaria caused by Urtica dioica, intradermal histamine and cold urticaria. The presence of the cellular triad with mast cells, dendritic (or satellite) cells and lymphocytes suggests a functional interaction of these cells. These findings support the possible existence of mechanisms in the dermis that may participate in protective and/or injurious vasocentric immune reactions.
authors.affiliation: Hospital do Servidor Público Estadual de São Paulo, São Paulo, Brazil. prcriado@uol.com.br
authors.forename: P R
authors.initials: PR
authors.lastname: Criado
authors.forename: R F J
authors.initials: RF
authors.lastname: Criado
authors.forename: N Y S
authors.initials: NY
authors.lastname: Valente
authors.forename: L B
authors.initials: LB
authors.lastname: Queiroz
authors.forename: J E C
authors.initials: JE
authors.lastname: Martins
authors.forename: C
authors.initials: C
authors.lastname: Vasconcellos
mesh_terms: D000328:Adult; D020405:Dermis / Q000098:blood supply* / Q000473:pathology / Q000648:ultrastructure*; D005260:Female; D006801:Humans; D007249:Inflammation; D008264:Macrophages / Q000648:ultrastructure; D008297:Male; D008407:Mast Cells / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008875:Middle Aged; D014581:Urticaria / Q000139:chemically induced* / Q000473:pathology*