Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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August 31, 2009
Adult Mitochondrial Encephalomyopathy: Diabetes Mellitus and Deafness
- Mitochondrial encephalomyopathies are a heterogeneous group of disorders with considerable phenotypic diversity and various respiratory chain biochemical defects affecting CNS.'Common diseases that can cause overlapping symptoms are endocrinopathies and collagen vascular diseases.
- Diagnosis can be made by clinical presentation and family history, routine laboratory tests, and molecular, genetic, pathologic, or biochemical data. Criteria for diagnosis require a known pathologic mutation and severe biochemical deficiency. The Thor-Byrne-ier scale represents a balanced approach to diagnosis but still leaves many patients out of the "definite" category.
- Diabetes mellitus and deafness affects presents in mid-childhood-to-late adolescence, with insulin-dependent diabetes mellitus developing in the 3rd-4th decades and and strokes. Muscle analysis shows functional defects of complexes I, III, and IV, but not complex II, being highly suggestive of a mtDNA disorder. Some cases are associated with A3243G mutation also seen with MELAS.
- Neuroimaging helps to suspect and in diagnosis as follows: detection of CNS lactate by MRS is useful as a high levels show good correlation with other markers of mitochondrial disease. Remember that because of differences in types of mitochondrial disorders, timing, severity and location of lesions, lactate may be undetected by MRS.