Prolonged myopathy and musculoskeletal symptoms following filgrastim in a 43-Year-Old female stem cell donor: a case-based review

Filgrastim, a granulocyte colony-stimulating factor (G-CSF), is widely used for the mobilization of peripheral blood stem cells in donors and is generally considered safe. While transient side effects such as bone pain and arthralgia are well-documented, chronic musculoskeletal complications are rarely reported, particularly in otherwise healthy individuals. Herein, we describe the case of a 43-year-old physically active female who developed prolonged musculoskeletal symptoms following stem cell mobilization with filgrastim. The patient initially experienced severe flu-like symptoms and diffuse myalgia, which progressed post-collection and significantly impaired daily function. Despite partial spontaneous improvement, symptoms recurred after physiotherapy and persisted nine months later, prompting hospital admission. Clinical findings included joint pain, swelling, and restricted shoulder mobility. Laboratory tests showed elevated inflammatory markers and positive ANA, while creatine kinase levels remained normal. Imaging revealed Klippel-Feil syndrome and mild degenerative changes. A single dose of intramuscular betamethasone led to gradual recovery of muscular function. This case underscores the importance of recognizing potential long-term iatrogenic effects of G-CSF, even in healthy donors, and highlights the need for individualized follow-up and management.