Mitochondrial encephalomyopathy lactic acidosis

MELAS mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes... 

MELAS, Mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes CPEO, chronic progressive external ophthalmoplegia LHON, Leber hereditary optic neuropathy NARP, neurogenic muscle weakness, ataxia, and retinitis pigmentosa NIDDM, non-insulin-dependent diabetes mellitus TER, termination. 

L12. Liou, C. W., Huang, C. C., Lin, T. K., Tsai, J. L., and Wei, Y. H., Correction of pancreatic /3-cell dysfunction with coenzyme Qio in a patient with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes syndrome and diabetes mellitus. Eur. Neurol. 43, 54-55 (2000). 

Figure 8-4. The effect of the MELAS mutation on mitochondrial function is to interfere with function of respiratory Complex I or I and IV, leading to increased levels of NADH and thus also of lactate. CoQ, coenzyme Q MELAS, mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes RC, respiratory complex.

This complex contains 11 polypeptide subunits of which only one is encoded by mtDNA. Defects of complex III are relatively uncommon and clinical presentations vary. Fatal infantile encephalomyopathies have been described in which severe neonatal lactic acidosis and hypotonia are present along with generalized amino aciduria, a Fanconi syndrome of renal insufficiency and eventual coma and death. Muscle biopsy findings may be uninformative since abnormal mitochondrial distribution is not seen, i.e., there are no ragged-red fibers. Other patients present with pure myopathy in later life and the existence of tissue-specific subunits in complex III has been suggested since one of these patients was shown to have normal complex 111 activity in lymphocytes and fibroblasts. 

MELAS (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes) resuits from a point mutation in the mitochondriai tRNA gene. 

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