Transient worsening of thyrotoxic myopathy following methimazole and metoprolol initiation in a 12-year-old girl: a case report and literature review
-
Yuto Onishi
,
Shinji Higuchi
,
Kohei Iwata
,
Yoh Watanabe
,
Yuki Yamada
und
Jun Mori
Abstract
Objectives
Thyrotoxic myopathy (TM) is a muscle disorder associated with hyperthyroidism. Although TM is common in adults, its incidence in children is unknown due to the limited number of reports. TM usually improves with the treatment of hyperthyroidism. This is the first report of a patient with TM who experienced transient worsening of muscle weakness shortly after administration of methimazole (MMI) and metoprolol tartrate.
Case Presentation
A 12-year-old Japanese girl with Graves’ disease was administered MMI and metoprolol tartrate. Within 12 h of treatment initiation, the patient experienced difficulty in standing from a chair. Examination revealed proximal lower-limb weakness and reduced grip strength. Based on the patient’s clinical course and blood test results, thyrotoxic periodic paralysis, myasthenia gravis, or polymyositis were considered unlikely. While the side effects of MMI and metoprolol tartrate were also considered as differential diagnoses, her history revealed mild pre-existing lower limb muscle weakness for 2 months before treatment, suggesting that the side effects of the medication were unlikely. Given the clinical course, the worsening of TM was the most probable cause, and treatment was continued cautiously. Muscle weakness gradually improved over 3 months as her thyroid hormone levels normalized. Magnetic resonance imaging taken 1 month later revealed gluteus muscle atrophy, which resolved within 10 months.
Conclusions
TM may show transient worsening after MMI and metoprolol tartrate administration, requiring the evaluation of TM, drug side effects, and other possible causes before continuing treatment. This case highlights the importance of recognizing TM in pediatric patients.
Acknowledgments
We thank the patient’s parents for providing consent for the publication of this case. We also thank Dr. Ichiro Kuki and Dr. Naoki Yamada for performing the nerve and muscle assessments and electromyography. Additionally, we thank Editage (www.editage.com) for their assistance with English language editing.
-
Research ethics: Not applicable.
-
Informed consent: Informed consent was obtained from the individual included in this study and her legal guardians.
-
Author contributions: Yuto Onishi served as the first author, contributing to the conception and design of the study, data collection and interpretation, and drafting of the manuscript. Shinji Higuchi, as the senior author, contributed to the study conception and design, data interpretation, manuscript drafting, and provided overall supervision. Jun Mori, as the last author, provided senior oversight, contributed to data interpretation, and critically revised the manuscript. Kohei Iwata, Yoh Watanabe, and Yuki Yamada contributed to data collection and interpretation and participated in the critical revision of the manuscript. All authors have accepted responsibility for the entire content of this manuscript and approved its submission.
-
Use of Large Language Models, AI and Machine Learning Tools: ChatGPT was used as an English proofreading service.
-
Conflict of interest: The authors have no conflicts of interest to declare.
-
Research funding: None declared.
-
Data availability: All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.
References
1. Kammer, GM, Hamilton, CRJr. Acute bulbar muscle dysfunction and hyperthyroidism. A study of four cases and review of the literature. Am J Med 1974;56:464–70. https://doi.org/10.1016/0002-9343(74)90477-x.Suche in Google Scholar PubMed
2. Duyff, RF, Van den Bosch, J, Laman, DM, van Loon, BJ, Linssen, WH. Neuromuscular findings in thyroid dysfunction: a prospective clinical and electrodiagnostic study. J Neurol Neurosurg Psychiatry 2000;68:750–5. https://doi.org/10.1136/jnnp.68.6.750.Suche in Google Scholar PubMed PubMed Central
3. Johnston, DM. Thyrotoxic myopathy. Arch Dis Child 1974;49:968–9. https://doi.org/10.1136/adc.49.12.968.Suche in Google Scholar PubMed PubMed Central
4. Chen, CC, Chiu, PC, Shih, CH, Hsieh, KS. Proximal weakness of lower limbs as the sole presentation of hyperthyroidism: report of one case. Acta Paediatr Taiwanica 2005;46:91–3.Suche in Google Scholar
5. Powell, A, Wilson, P, Powell, T. Case 4: chronic and progressive muscle weakness in a 9-year-old girl. Pediatr Rev 2019;40:647–9. https://doi.org/10.1542/pir.2017-0010.Suche in Google Scholar PubMed
6. Satam, N, More, V, Shanbag, P, Kalgutkar, A. Fatal thyrotoxic periodic paralysis with normokalemia. Indian J Pediatr 2007;74:1041–3. https://doi.org/10.1007/s12098-007-0194-8.Suche in Google Scholar PubMed
7. Perlman, SJ, Zaidman, CM. Childhood Graves disease masquerading as myasthenia gravis. J Child Neurol 2013;28:1309–11. https://doi.org/10.1177/0883073812457460.Suche in Google Scholar PubMed
8. Smółka, K, Perenc, L, Pelc, J, Smółka, L, Szajnik, K. Thyrotoxic myopathy with nonspecific ophthalmopathy in a two-year-old child: case report and literature review. J Clin Med 2024;13:6180. https://doi.org/10.3390/jcm13206180.Suche in Google Scholar PubMed PubMed Central
9. Greco, F, Caruso, M, Falsaperla, R, Fiumara, A, Parano, E. Ipertiroidismo ad insorgenza precoce con interessamento muscolare: descrizione di un paziente [Early-onset hyperthyroidism with muscle involvement: a report on a patient]. Pediatr Med e Chir 1996;18:611–3. Italian.Suche in Google Scholar
10. Cui, H, Zhang, X. Thyrotoxic myopathy: research status, diagnosis, and treatment. Endokrynol Pol 2022;73:157–62. https://doi.org/10.5603/EP.a2022.0004.Suche in Google Scholar PubMed
11. Wang, H, Li, H, Kai, C, Deng, J. Polymyositis associated with hypothyroidism or hyperthyroidism: two cases and review of the literature. Clin Rheumatol 2011;30:449–58. https://doi.org/10.1007/s10067-010-1570-8.Suche in Google Scholar PubMed
12. Bou Khalil, R, Abou Salbi, M, Sissi, S, El Kara, N, Azar, E, Khoury, M, et al.. Methimazole-induced myositis: a case report and review of the literature. Endocrinol Diabetes Metab Case Rep 2013;2013:130008. https://doi.org/10.1530/edm-13-0008.Suche in Google Scholar
13. Miernik, S, Matusiewicz, A, Olesińska, M. Drug-Induced myopathies: a comprehensive review and update. Biomedicines 2024;12:987. https://doi.org/10.3390/biomedicines12050987.Suche in Google Scholar PubMed PubMed Central
14. Lin, SH. Thyrotoxic periodic paralysis. Mayo Clin Proc 2005;80:99–105. https://doi.org/10.1016/s0025-6196(11)62965-0.Suche in Google Scholar
15. Puvanendran, K, Cheah, JS, Naganathan, N, Wong, PK. Thyrotoxic myopathy: a clinical and quantitative analytic electromyographic study. J Neurol Sci 1979;42:441–51. https://doi.org/10.1016/0022-510x(79)90177-1.Suche in Google Scholar PubMed
16. Couillard, P, Wijdicks, EF. Flaccid quadriplegia due to thyrotoxic myopathy. Neurocrit Care 2014;20:296–7. https://doi.org/10.1007/s12028-013-9940-0.Suche in Google Scholar PubMed
17. Tee, HC, Khoo, SSK, Fung, YK. Thyroid storm with acute flaccid quadriparesis due to thyrotoxic myopathy: a case report. J ASEAN Fed Endocr Soc 2020;35:118–21. https://doi.org/10.15605/jafes.035.01.20.Suche in Google Scholar PubMed PubMed Central
18. Shaheen, D, Kim, CS. Myositis associated with the decline of thyroid hormone levels in thyrotoxicosis: a syndrome? Thyroid 2009;19:1413–7. https://doi.org/10.1089/thy.2009.0014.Suche in Google Scholar PubMed
19. Li, Q, Liu, Y, Zhang, Q, Tian, H, Li, J, Li, S. Myopathy in hyperthyroidism as a consequence of rapid reduction of thyroid hormone: a case report. Medicine (Baltim) 2017;96. https://doi.org/10.1097/md.0000000000007591.Suche in Google Scholar PubMed PubMed Central
20. Lu, R, Wang, H, Hong, T, Gao, H. Myopathy after rapid correction of hyperthyroidism: a case report and review of literature. Medicine (Baltim) 2020;99. https://doi.org/10.1097/md.0000000000018878.Suche in Google Scholar
21. Salvatore, D, Simonides, WS, Dentice, M, Zavacki, AM, Larsen, PR. Thyroid hormones and skeletal muscle--new insights and potential implications. Nat Rev Endocrinol 2014;10:206–14. https://doi.org/10.1038/nrendo.2013.238.Suche in Google Scholar PubMed PubMed Central
22. Olson, BR, Klein, I, Benner, R, Burdett, R, Trzepacz, P, Levey, GS. Hyperthyroid myopathy and the response to treatment. Thyroid 1991;1:137–41. https://doi.org/10.1089/thy.1991.1.137.Suche in Google Scholar PubMed
23. Finsterer, J, Segall, L. Drugs interfering with mitochondrial disorders. Drug Chem Toxicol 2010;33:138–51. https://doi.org/10.3109/01480540903207076.Suche in Google Scholar PubMed
24. Scatena, R, Bottoni, P, Botta, G, Martorana, GE, Giardina, B. The role of mitochondria in pharmacotoxicology: a reevaluation of an old, newly emerging topic. Am J Physiol Cell Physiol 2007;293:C12–1. https://doi.org/10.1152/ajpcell.00314.2006.Suche in Google Scholar PubMed
25. Argov, Z, Mastaglia, FL. Drug therapy: disorders of neuromuscular transmission caused by drugs. N Engl J Med 1979;301:409–13. https://doi.org/10.1056/nejm197908233010805.Suche in Google Scholar
26. Uusitupa, M, Aro, A, Korhonen, T, Jukka, E. beta-Blockade, myopathy, and thyrotoxicosis. Br Med J 1980;280:183. https://doi.org/10.1136/bmj.280.6208.183.Suche in Google Scholar PubMed PubMed Central
27. Radetti, G, Paganini, C, Dordi, B, Gentili, L, Tomelleri, G. A case of persistent thyrotoxic myopathy. Eur J Pediatr 1996;155:623–4. https://doi.org/10.1007/s004310050455.Suche in Google Scholar
28. Drash, PW, Money, J. Motor impairment and hyperthyroidism in children: report of two cases. Dev Med Child Neurol 1966;8:741–5. https://doi.org/10.1111/j.1469-8749.1966.tb01835.x.Suche in Google Scholar PubMed
29. Jansson, R, Dahlberg, PA, Lindström, B. Comparative bioavailability of carbimazole and methimazole. Int J Clin Pharmacol Ther Toxicol 1983;21:505–10.Suche in Google Scholar
© 2025 Walter de Gruyter GmbH, Berlin/Boston
