The present study indicated that four Japanese patients in a Japanese pedigree who presented with epileptic spasms in early infancy, severe psychomotor retardation, and characteristic brain MRI findings of progressive brain atrophy and bilateral thalami and basal ganglia lesions were caused by homozygous mutation (c.958G > C, [p.E320Q]) in SLC19A3. Our cases broaden the phenotypic spectrum of disorders associated with SLC19A3 mutations and highlight the potential benefit of biotin and/or thiamin treatments and the need to assess the clinical efficacy of these treatments. This evidence concerns the gene SLC19A3 and Epileptic spasm.