Encephalo-myopathys are an multisistemic disorders which are characterize by mitochondrial biochemical and genetic disfunction with variable heredity. One of the most frequent diseases from this group of disorders is mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke (MELAS) which is an maternal hereditary. The strokelike episodes characterize this sindrom. Other features, such as seizures, diabetes mellitus, hearing loss, short stature, and exercise intolerance are clearly part of the disorder Approximately 80% of patients with the clinical characteristics of MELAS have a heteroplasmic A-to-G point mutation in the dihydrouridine loop of the transfer RNA (tRNA)Leu (UUR) gene. In this study, we will try to realize an algoritm of diagnostic starting from an patient with susceptibility of MELAS. In the young patient with multiple stroke-like episodes in different vascular territories and neuroradiology features of transient abnormalities in varying regions, seizures, neuromuscular deficit, short stature, gastrointestinal, ophthalmologycal affectation, laboratory testing for MELAS must be performed. The presence of ragged red fibers in skeletal muscle and biochemical demonstration of defects in mitochondrial respiratory enzymes strongly support the diagnosis. Molecular genetic testing for abnormalities in mitochondrial DNA will confirm the diagnosis. Genetic counseling should be provided to patients with MELAS associated with mitochondrial DNA point mutations.