Alexander disease is a leukoencephalopathy that usually presents during infancy with developmental delay, macrocephaly and seizures. Several sequencing analyses have identified mutations in the gene encoding glial fibrillary acidic protein (GFAP) of patients with Alexander disease. We described a girl who developed seizures in infancy with atypical CT findings and in whom a novel heterozygous mutation, L90P (283T --> C), was detected in exon 1 of the GFAP gene. The neurological deterioration was mild and appeared relatively late for infantile onset.