title: Leukopenia due to parvovirus B19 in a Crohn's disease patient using azathioprine.
abstract: Thiopurines such as azathioprine (AZA) and 6-mercaptopurine are frequently used for the treatment of inflammatory bowel diseases. Patients with low or absent thiopurine S-methyltransferase (TPMT) activity, resulting in high 6-thioguanine nucleotide levels, have an increased risk of developing leukopenia. Alternatively, certain viral infections could induce leukopenia. We present the case of an adult Crohn's disease patient with a parvovirus B19 infection and leukopenia during long-term AZA therapy. The uncomplicated long-term use of adequately-dosed AZA and stable non-toxic metabolite levels could not acknowledge TPMT deficiency as a primary cause of the leukopenia. parvovirus B19 was assumed to induce the leukopenia by restraining myeloid proliferation. In addition, AZA probably potentiated susceptibility to this viral infection and may have inhibited adequate immunological defense. Leukopenia during thiopurine therapy not explained by TPMT deficiency could be induced by parvovirus B19 infection and compels temporal but not permanent cessation of thiopurine therapy.
authors.affiliation: Department of Gastroenterology and Hepatology, VU University Medical Center, Amsterdam, The Netherlands. d.vanasseldonk@vumc.nl
authors.forename: Dirk P
authors.initials: DP
authors.lastname: van Asseldonk
authors.forename: Bernardina M
authors.initials: BM
authors.lastname: Kanis
authors.forename: Nanne K H
authors.initials: NK
authors.lastname: de Boer
authors.forename: Ad A
authors.initials: AA
authors.lastname: van Bodegraven
mesh_terms: D000328:Adult; D001379:Azathioprine / Q000009:adverse effects*; D003424:Crohn Disease / Q000150:complications / Q000188:drug therapy*; D016731:Erythema Infectiosum / Q000209:etiology* / Q000821:virology; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000009:adverse effects*; D007970:Leukopenia / Q000821:virology*; D016732:Parvovirus B19, Human
chemical_list: D007166:Immunosuppressive Agents; D001379:Azathioprine