UQCRC2 and metabolic acidosis: Furthermore, the variant in UQCRC2 is related to Mitochondrial complex III deficiency, nuclear type 5, which is a mitochondrial respiratory chain disorder characterized by highly variable clinical phenotypes including mitochondrial encephalopathy, psychomotor delay, ataxia, severe dysplasia, liver dysfunction, metabolic acidosis, renal tubular disease, muscle weakness and exercise intolerance (Hernando et al., 2002; Ballif et al., 2007; Bansept et al., 2023).