Of these 29 patients, eleven had mitochondrial disease confirmed on further genetic analysis, either with the presence of mtDNA rearrangements or deletions (n = 3) or with the identification of specific mutations (m.8719G > A, p. Gly65* (MTATP6), m.9185 T > C, p. Leu220Pro (MTATP6), m.3243A > G (MTTL1), m.7510 T > C (MTTS1), c.811C > T, p.R271C/c.911G > A, pA304T (CABC1/ADCK3) as well as compound heterozygosity for two sequence variants in the POLG gene (c.1232 T > C, p. (Leu411Pro) and c.1721G > A, p. (Arg574Gln)). Here, POLG is linked to inborn mitochondrial metabolism disorder.