Figure 2. MRI characteristics of POLR3-related leukodystrophy caused by POLR1C mutations.

Axial T2-weighted (a,b,d,e,g,h) and sagittal T1-weighted (c,f,i) images of case 1 aged 6 years (a–c) and case 2 aged 4.5 years (d–f) compared with a healthy control aged 4 years (g–i). Diffuse hyperintense signal of the supratentorial (red arrow, a,d) and cerebellar (blue arrow, b,e) white matter is visible on the T2-weighted images, indicating hypomyelination. There is no cerebellar atrophy. As typical for POLR3-related leukodystrophy, the ventrolateral thalamus (white arrow, a,d), the optic radiation (thick arrowhead blue, d) and the dentate nucleus (open red arrowhead, b) show a relative hypointense signal on the T2-weighted images resulting in an easily visible dentate nucleus (b) as compared with the control (h) as well as a small dot in the posterior limb of the internal capsule (red arrowhead, d). The corpus callosum is slightly thinned in case 1 and thinned in case 2 (open red arrowhead, c,f).