Acylcarnitine analysis is a useful investigation in other cases of suspected mitochondrial disease, since it may help to direct diagnostic genetic investigations, for example succinyl and propionyl carnitines may be elevated in patients with succinyl-CoA ligase deficiency caused by SUCLA2 or SUCLG1 mutations [38,39]. The gene discussed is SUCLG1; the disease is hyperinsulinemic hypoglycemia, familial, 4.