ECHS1 and hyperinsulinemic hypoglycemia, familial, 4: The previous quantitative analyses of patients with ECHS1 deficiency suggest that the accumulation of cysteine and cysteamine conjugates from valine intermediate to methacrylyl-CoA and acryloyl-CoA are responsible for the neuronal cytotoxicity, leading to basal ganglia lesions [11, [9], [13].