Novel mutation in mitochondrial DNA in 2 siblings with Leigh syndrome.

Leigh syndrome is clinically and genetically heterogeneous, associated with mutations in mitochondrial and nuclear genes.(1) Diagnostic criteria include progressive disorder with motor and intellectual delay/regression; signs and symptoms of brainstem and/or basal ganglia disease; raised lactate concentration in blood and/or CSF; and one or more of the following: (1) characteristic features on neuroimaging (bilateral symmetrical hyperintensities in brainstem, basal ganglia, dentate nuclei, and optic nerves on T2-weighted MRI); (2) typical neuropathologic changes; and (3) typical neuropathology in a similarly affected sibling.(2) We describe 2 African American siblings who have a mutation in the mitochondrial MT-TL2 gene and a clinical diagnosis of Leigh syndrome. The same mutation is also identified in their neurologically asymptomatic mother.