SCO1 and Global developmental delay: The biallelic variants in the SCO1 gene were associated with “mitochondrial complex 4 deficiency, nuclear type 4” (#619048), a metabolic disorder characterized by hypotonia, developmental delay, encephalopathy, hypertrophic cardiomyopathy, hepatomegaly, hepatic steatosis, hepatic failure, feeding difficulties, increased serum lactate, and metabolic acidosis.