Imatinib-Induced Myopathy in a Patient With Gastrointestinal Stromal Tumor: A Case Report

Abstract

Gastrointestinal stromal tumors (GISTs) are a neoplasm derived from interstitial cells of Cajal in the gastrointestinal tract. These tumors arise secondary to mutations in the KIT tyrosine kinase gene. First-line treatment for GISTs is imatinib, a selective tyrosine kinase inhibitor that blocks the function of the aberrant protein that drives the tumor. Imatinib is generally well-tolerated, with the most common adverse effects including nausea/vomiting, diarrhea, and edema. We present a case of a 68-year-old man who developed acute inflammatory demyelinating polyneuropathy (AIDP) with superimposed myositis following treatment of BRAF-wild type GIST with imatinib. Although myopathic adverse effects have been documented with other tyrosine kinase inhibitors, myopathy as an adverse effect of imatinib is rarely documented in the literature. This case highlights a rare but significant neuromuscular complication potentially linked to imatinib and emphasizes the importance of prompt recognition, thorough diagnostic workup, and interdisciplinary management.

Keywords: acute inflammatory demyelinating polyneuropathy; gastrointestinal stromal tumor; imatinib; immunotherapy; myositis.

Figure 1. Creatine Kinase Values

Note: Imatinib was held, and corticosteroids were initiated on Day 0. Plasmapheresis was initiated following the discontinuation of creatine kinase monitoring.