BACKGROUND: MELAS (mitochondrial myopathy, lactic acidosis and stroke-like episodes) is one of the most common mitochondrial encephalomyopathies. MATERIAL/METHODS: We present four children with A3243G MELAS mtDNA mutation and give a summary of clinical MELAS symptoms reported in the literature. Serum lactate elevation, mosaic pattern of COX deficit and decreased activity of complex I and IV in the muscle biopsy were found in all cases. RRFs were recognized in three out of four. RESULTS: The main features seen in all our patients were poor growth and fatigability with muscle weakness. All presented epileptic jerks of various character, some deformation features (recurrent pretibial and peritarsal edema, large swollen-looking hands and feet, hypertelorism and protruding ears) and some cutaneous lesions (atopic dermatitis, local melanoderma, asymmetric vascular dilatation). Stroke-like episodes, multihormonal hypopituitarism, sensorineural hypoacusis, pigmentary retinal degeneration, intracranial calcification, heart involvement, recurrent vomiting or abdominal pain were seen only in individual cases. The homonymous hemianopia frequently reported in the literature was not a feature of our patients. One of them suffered from nonspecific sialoadenitis never mentioned in the literature. CONCLUSIONS: Morphological, enzymatic and molecular investigations of a muscle biopsy sample should be undertaken to improve early MELAS detection in patients with any multiorgan disease associated with serum lactate elevation.

Keywords: MELAS Syndrome - diagnosis, MELAS Syndrome - genetics