title: The Impact of Azathioprine-Associated Lymphopenia on the Onset of Opportunistic Infections in Patients with Inflammatory Bowel Disease.
abstract: Thiopurines are known to cause lymphopenia (<1,500 lymphocytes/μl). As severe lymphopenia (<500C/μl) is associated with opportunistic infections, we investigated severity of thiopurine-related lymphopenia and development of opportunistic infections in our tertiary referral centre.
  
  
  
  We retrospectively screened medical records of 1,070 IBD patients and identified 100 individuals that developed a total of 161 episodes of lymphopenia during thiopurine treatment between 2002 and 2014. Occurrence of opportunistic infections was documented. A control group consisted of IBD patients receiving thiopurines but without developing lymphopenia.
  
  
  
  Of a total of 161 episodes of lymphopenia, 23% were severe (<500C/μl). In this subgroup, thiopurine dosing was modified in 64% (dosage reduction: 32%, medication discontinued: 32%). We identified 9 cases (5.5%) of opportunistic infections, of which only two occurred during severe lymphopenia. One opportunistic infection (4.5%) was identified in the control group. No association was found between opportunistic infections and severity of lymphopenia. All patients who suffered from opportunistic infections were receiving additional immunosuppressive medication.
  
  
  
  Our patients treated with thiopurines rarely developed severe lymphopenia and opportunistic infections did not occur more often than in the control group. A careful monitoring of lymphocytes and prophylactic adjustment of thiopurine therapy might contribute to this low incidence.
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Marius
authors.initials: M
authors.lastname: Vögelin
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Luc
authors.initials: L
authors.lastname: Biedermann
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Pascal
authors.initials: P
authors.lastname: Frei
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.|Division of Gastroenterology and Hepatology, Stadtspital Triemli, Zurich, Switzerland.|Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
authors.forename: Stephan R
authors.initials: SR
authors.lastname: Vavricka
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Scharl
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Jonas
authors.initials: J
authors.lastname: Zeitz
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.|Division of Gastroenterology and Hepatology, Kantonsspital St. Gallen, St. Gallen, Switzerland.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Sulz
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.|Division of Gastroenterology and Hepatology, Stadtspital Triemli, Zurich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Fried
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.|Division of Gastroenterology and Hepatology, Stadtspital Triemli, Zurich, Switzerland.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Rogler
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.|Division of Gastroenterology and Hepatology, Stadtspital Triemli, Zurich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Scharl
mesh_terms: D000293:Adolescent; D000328:Adult; D001379:Azathioprine / Q000009:adverse effects* / Q000627:therapeutic use; D016022:Case-Control Studies; D002648:Child; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000009:adverse effects* / Q000627:therapeutic use; D015994:Incidence; D015212:Inflammatory Bowel Diseases / Q000188:drug therapy* / Q000453:epidemiology*; D008231:Lymphopenia / Q000139:chemically induced* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D009894:Opportunistic Infections / Q000139:chemically induced / Q000453:epidemiology*; D012189:Retrospective Studies; D012307:Risk Factors; D055815:Young Adult
chemical_list: D007166:Immunosuppressive Agents; D001379:Azathioprine