DARS2 and Leukoencephalopathy: In addition, the parents were both heterozygous for a pathogenic variant in DARS2 (NM_018122.5): c.788G>A; p.(Arg263Gln) known to cause leukoencephalopathy with brain stem and spinal cord involvement and lactate elevation (Online Mendelian Inheritance in Man: 611105) with autosomal recessive inheritance.