Case: An abdominal aortic aneurysm is rarely seen in children. We report the case of a 15-year-old girl who presented with lower back pain in a subfebrile setting with moderate biological inflammatory syndrome. Imaging assessment, including a spinal magnetic resonance imaging, had shown no evidence of spondylodiscitis or other spinal or renal pathology. Ten days later, she presented in hemorrhagic shock and was found to have a ruptured infected aneurysm of the abdominal aorta. Conclusions: This case reminds us to include an aneurysm in the differential diagnosis of lower back pain, even in children.