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Azathioprine-induced pancytopenia with normal TPMT activity presenting with HSV oral ulcers
  1. Caroline H Jensen1,
  2. John Tiu2,
  3. Jillian S Catalanotti2
  1. 1School of Medicine and Health Sciences, George Washington University, Washington, District of Columbia, USA
  2. 2Department of Medicine, George Washington University, Washington, District of Columbia, USA
  1. Correspondence to Caroline H Jensen, jensenc{at}


A 65-year-old man with treatment-resistant psoriatic arthritis, hypertension, dyslipidaemia and benign prostatic hyperplasia (BPH) presented with herpes simplex virus (HSV) oral ulcers and a recent 15 lb weight loss due to reduced consumption. Five weeks previously, his methotrexate was tapered and he had begun taking azathioprine. The patient’s thiopurine S-methyltransferase (TPMT) activity level was normal prior to starting azathioprine. He was found to have pancytopenia with normal folate levels and azathioprine was discontinued. His pancytopenia worsened, with a nadir 8 days after stopping azathioprine, before returning to normal levels. His oral ulcers improved and he was able to tolerate solid food. This case illustrates that decreased TPMT activity is not the only risk factor for pancytopenia as an adverse reaction to azathioprine. Furthermore, HSV stomatitis may be the presenting symptom of pancytopenia. The timeline of improvement in cell counts illustrated in this patient has implications for the management of suspected azathioprine-induced pancytopenia.

  • unwanted effects / adverse reactions
  • contraindications and precautions
  • safety
  • haematology (drugs and medicines)
  • malignant disease and immunosuppression

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  • Contributors CHJ conceived the project and drafted the initial manuscript. She obtained the patient’s consent for the case report and was responsible for incorporating the other authors’ revisions and submitting the final work. JT was involved in the planning and conception of the project, acquisition of patient consent and data and revising the manuscript. JSC was involved in the planning, background research, analysis of data and editing of the manuscript. All authors were involved in the care of the patient. All authors approved the submitted manuscript and agree to be accountable for all aspects of the work.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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