POLR3B and leukodystrophy: This might be explained by a viewpoint that diffuse hypomyelination was not an obligatory feature for 4H leukodystrophy that had reported in previous study.[14] Considering ambulation without wheelchair and normal cognition in our patients, we also thought clinical phenotype of POLR3B mutation patients were lighter than POLR3A mutation which was also in keeping with the opinion from previous research.[13]