MECP2 and Down syndrome: The following etiologies were identified in 16 patients: tuberous sclerosis complex (n = 5), post-acute encephalopathy (n = 3), hippocampal sclerosis (n = 1), focal cortical dysplasia (n = 1), chemotherapy-induced leukoencephalopathy (n = 1), methyl-CpG binding protein 2 (MECP2) duplication syndrome (n = 1), post-neonatal hypoxic-ischemic encephalopathy (n = 1), very-long-chain acyl-CoA dehydrogenase deficiency (n = 1), Down syndrome (n = 1), and post-neonatal hypoglycemia (n = 1).