Clinical and genetic uniqueness in an individual with MELAS.

Mitochondrial encephalopathy lactic acidosis stroke like episodes (MELAS) is a progressive neurodegenerative disorder with varying age of onset. It is a clinically and genetically heterogeneous disease. Molecular etiology of MELAS is not known in several cases. We have identified a unique individual with late onset MELAS at the age of 55 years. We have analyzed the complete mitochondrial genome of the tissue and blood samples of the patient. One novel heteroplasmic mutation (C13565A) in NADH dehydrogenase 5 subunit (ND5) gene was found only in the tissue sample but not in the blood. This mutation is missense causing a change of amino acid serine to tyrosine at position 410. This mutation was found neither in controls nor in world populations. This study has also confirmed ND5 as a hotspot for the mitochondrial diseases. This will be of great help for the clinicians in the diagnosis of MELAS.