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Endocrinology
Minimal methimazole exposure-induced fatal pancytopenia
  1. Xiu Ying Au,
  2. Patricia L Kapsner,
  3. Nancy Shrestha and
  4. David Schade
  1. Internal Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, USA
  1. Correspondence to Dr David Schade; DSchade{at}salud.unm.edu

Abstract

This case highlights that refractory pancytopenia leading to death can occur with methimazole treatment even at a very low cumulative dose and after a very short duration of exposure. In addition, the standard treatments to correct the pancytopenia may not be effective and a bone marrow transplant may be required. Current American Thyroid Association guidelines do not recommend routine monitoring of the complete blood count in patients receiving thionamides because of the rapidity of the onset of agranulocytosis and the lack of positive evidence that such monitoring would be useful. Patient education concerning the clinical adverse effects of pancytopenia should be stressed before drug initiation. Patients should discontinue thionamides immediately and seek medical treatment if they develop anaemia, fever, pharyngitis, severe infection or easy bruising. Physicians need to be aware that pancytopenia from methimazole is not dose-related and be alert to any patient signs or symptoms of infection. Subspecialty consultation will be required.

  • Immunology
  • Thyroid
  • Thyroiditis
  • Thyrotoxicosis

https://doi.org/10.1136/bcr-2024-261106

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    Footnotes

    • Contributors The following authors were responsible for drafting of the text, sourcing and editing of clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content: DS, XYA, PLK, NS. The following authors gave final approval of the manuscript: DS, XYA, PLK, NS. The policies of the Department of Internal Medicine and its chair, and the Ethics Committee, University of New Mexico, have approved the publication of this manuscript. DS is the guarantor.

    • 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.

    • Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.

    • Competing interests None declared.

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