
==== Front
Intern Med
Intern Med
Internal Medicine
0918-2918
1349-7235
The Japanese Society of Internal Medicine

38220194
10.2169/internalmedicine.2939-23
Pictures in Clinical Medicine
Regorafenib-induced Myopathy
Ochiai Shuya 1
Ueno Tatsuya 1
Igarashi Shohei 2
Arai Akira 1
1 Department of Neurology, Aomori Prefectural Central Hospital, Japan
2 Department of Gastroenterology, Aomori Prefectural Central Hospital, Japan
Correspondence to Shuya Ochiai, jichisanbongi@gmail.com

13 1 2024
15 8 2024
63 16 23432344
19 9 2023
27 11 2023
Copyright © 2024 by The Japanese Society of Internal Medicine
https://creativecommons.org/licenses/by-nc-nd/4.0/ The Internal Medicine is an Open Access journal distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. To view the details of this license, please visit (https://creativecommons.org/licenses/by-nc-nd/4.0/).
regorafenib
myopathy
short tau inversion recovery
colon cancer
==== Body
pmcA 45-year-old man presented with a gait disturbance due to bilateral muscle pain. Grasping pain was observed in both lower extremities with grade 3 muscle strength. Regorafenib had been initiated 10 days earlier for sigmoid colon cancer. The patient had no history of autoimmune disease or programmed-death-receptor-1/immune-checkpoint inhibitor therapy. Although inflammatory markers (C-reactive-protein and erythrocyte-sedimentation-rate) were mildly elevated, muscle injury biomarker levels (creatine-kinase, myoglobin, and aldolase) were normal. Autoimmune-related antibodies (antinuclear-antibody, anti-double-stranded-deoxyribonucleic-acid, myeroperoxydase-anti-neutrophil-cytoplasmic-antibodies, proteinase-3-anti-neutrophil-cytoplasmic-antibodies, anti-Jo-1, and anti-aminoacyl-tRNA-synthetase) were negative. Electromyography revealed fibrillation potentials and positive sharp waves in the right vastus lateralis muscle. Short tau inversion recovery (STIR)-magnetic resonance imaging (MRI) showed hyperintense lesions, mainly in the anterior thigh muscles (Picture a, b, arrowheads). The patient was diagnosed with regorafenib-induced myopathy. Four weeks after regorafenib discontinuation, the symptoms and STIR-MRI abnormalities had improved (Picture c, d). Regorafenib-associated myopathy is rare (1,2). To our knowledge, this is the first report of MRI findings of regorafenib-induced myopathy. If muscle pain or weakness develops after regorafenib administration, clinicians should look for MRI signal changes.

Picture.

Written informed consent was obtained from the patient.

The authors state that they have no Conflict of Interest (COI).
==== Refs
1. Mir O , Brodowicz T , Italiano A , et al . Safety and efficacy of regorafenib in patients with advanced soft tissue sarcoma (REGOSARC): a randomised, double-blind, placebo-controlled, phase 2 trial. Lancet Oncol 17 : 1732-1742, 2016.27751846
2. Yang Y , Xu L , Wang D , et al . Anti-PD-1 and regorafenib induce severe multisystem adverse events in microsatellite stability metastatic colorectal cancer: a case report. Immunotherapy 13 : 1317-1323, 2021.34369830
