For example, among the mutations that affect the CNS, there is a strong correlation between early onset of disease and the severity of the clinical symptoms, illustrated by the contrast between DARS2-associated leukoencephalopathies, which present as LBSL disease and RARS2-associated epileptic encephalopathy, which presents as pontocerebellar hypoplasia type 6 (PCH6). Here, DARS2 is linked to pontocerebellar hypoplasia type 6.