Granulocyte colony-stimulating factor-induced hypersensitivity reaction with leukocytosis in a pediatric germ cell tumor patient: a case report

Chemotherapy-induced bone marrow suppression significantly increases the risk of febrile neutropenia (FN) in cancer patients. Granulocyte colony-stimulating factor (G-CSF) is a cornerstone therapy for FN prophylaxis and treatment that promotes myeloid progenitor cell proliferation and differentiation, thereby reducing the duration of neutropenia. While G-CSF is generally well tolerated and has a favorable safety profile, rare but life-threatening adverse events may occur.

We present the case of a 14-year-old female with a germ cell tumor who developed a systemic hypersensitivity reaction following prophylactic administration of efbemalenograstim alfa-vuxw (20 mg/dose) after her third chemotherapy cycle. Notably, the patient had previously tolerated two full doses of efbemalenograstim alfa-vuxw and one full dose of short-acting G-CSF (filgrastim biosimilar 5 μg/kg) without any adverse events during the first two chemotherapy cycles. Within two hours post-injection, she exhibited severe hypotension (74/52 mmHg), hypoxemia (SpO₂ 81%), and marked leukocytosis (55.32 → 104.25 × 10⁹/L within 24 h). Emergency intervention with epinephrine and dexamethasone resolved the symptoms. Peripheral blood analysis revealed eosinophilia (0.16 × 10⁹/L), suggesting drug sensitization. During the fourth chemotherapy cycle, subcutaneous recombinant human G-CSF (rhG-CSF, filgrastim biosimilar; 5 μg/kg) was administered, but the patient experienced a nearly identical reaction within 30 min (BP 53/29 mmHg, SpO₂ 97%). The temporal correlation and clinical consistency confirmed a G-CSF-induced systemic hypersensitivity reaction.

To our knowledge, this represents the first documented pediatric case of recurrent systemic hypersensitivity reactions induced by sequential administration of different G-CSF formulations following chemotherapy. Notably, long-acting G-CSF (efbemalenograstim alfa-vuxw) was associated with both hypersensitivity and pronounced leukocytosis. Our findings highlight the following: 1. Hypersensitivity to G-CSF, although rare, requires heightened clinical vigilance; 2. The Substitution of G-CSF products may not preclude recurrent reactions; 3. The safety profile and optimal dosing of efbemalenograstim alfa-vuxw in pediatric populations warrant further validation in controlled trials.