Myalgia and Rigidity as Adverse Effects of Trametinib Therapy

Mitogen-activated extracellular kinase inhibitors, including trametinib and selumetinib, are increasingly used to treat pediatric low-grade gliomas. Trametinib, while administered orally and with minimal myelosuppression, is reported to cause rash, diarrhea, and fatigue. Selumetinib has been associated with skin irritation, diarrhea, and musculoskeletal pain. This case report describes an 8-month-old male with a low-grade glioma (LGG) that progressed 6 months post-chemotherapy and was started on trametinib due to its liquid formulation and minimal side effect profile. However, the patient developed severe diarrhea, abdominal pain, neck pain, rigidity, and decreased stamina. These symptoms necessitated discontinuation of trametinib, after which all symptoms resolved within a week. This case highlights the first reported instance of trametinib-induced myalgia and rigidity in a pediatric patient receiving trametinib therapy for a LGG. Clinicians should consider these rare but significant adverse effects when choosing an antineoplastic therapy for the treatment of progressive LGG.