POLR1C and leukodystrophy: All 14 patients had a confirmed diagnosis of POLR3-HLD based on their clinical and radiological features in addition to the molecularly confirmed presence of likely pathogenic or pathogenic variants in POLR3A or POLR1C. Thirteen patients had biallelic variants in POLR3A (92.9%), and one had biallelic variants in POLR1C (7.1%; Table 2).