MT-ND1 and Leigh syndrome: For the third patient, we report a novel pathogenic variant m.3955G>A p.(Ala217Thr) in MT-ND1 as a new cause of Leigh syndrome in a boy who presented at 2 months with an early infantile epileptic encephalopathy, lactic acidosis, and brain MRI demonstrating bilateral symmetrical signal abnormality involving the caudate nuclei, putamina, midbrain, medulla, upper cervical cord, and perirolandic cortex.