title: Azathioprine Hypersensitivity Syndrome: Two Cases of Febrile Neutrophilic Dermatosis Induced by Azathioprine.
abstract: BACKGROUND
  Azathioprine is an immunosuppressive agent used in the treatment of immune-mediated diseases. Azathioprine hypersensitivity syndrome is a rare adverse reaction occurring a few days to weeks after the administration of azathioprine.
  
  
  METHODS
  A 36-year-old male with ulcerative colitis presented with erythematous plaques, pustules and erosions on the lower back, buttocks and thighs associated with high fever (39°C) 2 weeks after the initiation of azathioprine 100 mg/day. Additional findings included leukocytosis (18.6 g/L) with neutrophilia (11.1 g/L) and elevated C-reactive protein (128 mg/L). Histopathology showed a dense infiltrate of neutrophils in the hair follicles. We increased the dose of prednisone to 1 mg/kg/day (60 mg/day) and azathioprine was discontinued. He had marked improvement within 3 weeks and did not have any relapse with a 1-year follow-up.
  
  
  METHODS
  A 57-year-old male with ulcerative colitis presented with erythematous plaques and pustules on the lower limbs associated with high fever (40°C) 1 week after the initiation of azathioprine 75 mg/day. Leukocytosis with neutrophilia (13.6 g/L) and elevated C-reactive protein (344 mg/L) were among the laboratory findings. Histopathology showed a dense infiltrate of neutrophils in the hair follicles. The dose of prednisone was increased to 20 mg/day and azathioprine was discontinued, which led to complete remission within 7 days. He did not have any relapse with a 6-month follow-up.
  
  
  CONCLUSIONS
  The development of acute neutrophilic dermatitis 2 weeks after the initiation of azathioprine and the complete resolution after its withdrawal were in favor of azathioprine hypersensitivity syndrome. It should not be confused with Sweet syndrome associated with inflammatory bowel disease, as maintenance of azathioprine treatment may lead to life-threatening reactions.
authors.affiliation: Paul Sabatier University, University Hospitals of Toulouse, Toulouse, France; Department of Dermatology, University Hospitals of Toulouse, Toulouse, France.
authors.forename: Majed
authors.initials: M
authors.lastname: Aleissa
authors.affiliation: Paul Sabatier University, University Hospitals of Toulouse, Toulouse, France; Department of Dermatology, University Hospitals of Toulouse, Toulouse, France.
authors.forename: Perrine
authors.initials: P
authors.lastname: Nicol
authors.affiliation: Paul Sabatier University, University Hospitals of Toulouse, Toulouse, France; Department of Dermatology, University Hospitals of Toulouse, Toulouse, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Godeau
authors.affiliation: Paul Sabatier University, University Hospitals of Toulouse, Toulouse, France; Department of Histopathology, University Hospitals of Toulouse, Toulouse, France.
authors.forename: Emilie
authors.initials: E
authors.lastname: Tournier
authors.affiliation: Cabinet De Bellisen Polyclinique, Carcassonne, France.
authors.forename: Frederic
authors.initials: F
authors.lastname: de Bellissen
authors.affiliation: Paul Sabatier University, University Hospitals of Toulouse, Toulouse, France; Department of Gastroenterology, University Hospitals of Toulouse, Toulouse, France.
authors.forename: Marie-Angèle
authors.initials: MA
authors.lastname: Robic
authors.affiliation: Paul Sabatier University, University Hospitals of Toulouse, Toulouse, France; Department of Dermatology, University Hospitals of Toulouse, Toulouse, France.
authors.forename: Cristina Bulai
authors.initials: CB
authors.lastname: Livideanu
authors.affiliation: Paul Sabatier University, University Hospitals of Toulouse, Toulouse, France; Department of Dermatology, University Hospitals of Toulouse, Toulouse, France.
authors.forename: Juliette
authors.initials: J
authors.lastname: Mazereeuw-Hautier
authors.affiliation: Paul Sabatier University, University Hospitals of Toulouse, Toulouse, France; Department of Dermatology, University Hospitals of Toulouse, Toulouse, France.
authors.forename: Carle
authors.initials: C
authors.lastname: Paul
keywords: Azathioprine; Azathioprine hypersensitivity syndrome; Drug reaction; Inflammatory bowel disease; Neutrophilic dermatosis; Sweet syndrome