Alexander disease (AxD) is a rare and fatal leukodystrophy caused by a dominant missense mutation in the gene encoding glial fibrillary acidic protein (GFAP). Although the neuropathology of this disease is unclear, recent experimental studies in AxD model mice suggest that an inflammatory environment in the brain might play an important role in neuronal dysfunction. Here, we present a case of infantile AxD developed at the age of 3 months, which was diagnosed from MRI findings and by detection of a novel mutation (c. 1058 T>C) of the GFAP gene. Analysis of cytokines in the cerebrospinal fluid (CSF) revealed markedly high levels of interleukin (IL)-6, IL-8, and macrophage chemotactic protein 1 (MCP-1) at the time of onset. Previous studies in animal models of AxD show that MCP-1 levels in the CSF increase quickly at an early stage. In addition, although anti-epileptic drugs had little effect, steroid pulse therapy reduced (albeit transiently) epileptic activity and slowed progression of MRI white matter lesions. Here, we identified am association between clinical manifestations and the level of the cytokines in the CSF after steroid pulse therapy. Inflammatory responses might therefore be an important factor underlying this condition, resulting in both progressive white matter lesions and epileptic activity. Thus, it might be desirable to treat such patients with robust immunomodulation therapy to suppress inflammation of an infantile AxD.