Purpose <p>Spinal epidural lipomatosis (SEL) is a relatively rare condition characterized by overgrowth of adipose tissue in the extradural space of the spinal canal. Compression of neural structures can lead to radiculopathy, loss of sensation and motor function, and urinary retention. Known causes of SEL include exogenous steroid use and obesity.</p> Methods <p>We describe the unique case of idiopathic SEL in a 1-year-old male, the youngest reported to date, diagnosed with medulloblastoma and treated with chemotherapy and autologous stem cell rescue (AuSCR). We then perform a systemic review of the literature of this rare diagnosis, explore potential causes, and review management.</p> Results <p>The patient was non-obese and received a cumulative dose of only 60&#xa0;mg dexamethasone (150&#xa0;mg/m²), far below pediatric cancer patients with SEL documented in the literature. The acute presentation of lipomatosis following chemotherapy and AuSCR, associated with transient elevated triglycerides (234&#xa0;mg/dL), suggests this as a possible cause.</p> Conclusion <p>This case illustrates the development and resolution of SEL in a non-obese pediatric cancer patient with limited steroid use. While further study is needed to identify the etiology of SEL, this diagnosis should be evaluated for when reviewing spine imaging following chemotherapy or autologous stem cell rescue.</p>