Neurological mitochondrial cytopathies

The mitochondrial cytopathies are genetically and phenotypically heterogeneous group of disorders caused by structural and functional abnormalities in mitochondria. To the best of our knowledge, there are very few studies published from India till date. Selected and confirmed fourteen cases of neurological mitochondrial cytopathies with different clinical syndromes admitted between 1997 and 2000 are being reported. There were 8 male and 6 female patients. The mean age was 24.42+/-11.18 years (range 4-40 years). Twelve patients could be categorized into well-defined syndromes, while two belonged to undefined group. In the defined syndrome categories, three patients had MELAS (mitochondrial encephalopathy, lactic acidosis and stroke like episodes), three had MERRF (myoclonic epilepsy and ragged red fibre myopathy), three cases had KSS (Kearns-Sayre Syndrome) and three were diagnosed to be suffering from mitochondrial myopathy. In the uncategorized group, one case presented with paroxysmal kinesogenic dystonia and the other manifested with generalized chorea alone. Serum lactic acid level was significantly increased in all the patients (fasting 28.96+/-4.59 mg%, post exercise 41.02+/-4.93 mg%). Muscle biopsy was done in all cases. Succinic dehydrogenase staining of muscle tissue showed subsarcolemmal accumulation of mitochondria in 12 cases. Mitochondrial DNA study could be performed in one case only and it did not reveal any mutation at nucleotides 3243 and 8344. MRI brain showed multiple infarcts in MELAS, hyperintensities in putaminal areas in chorea and bilateral cerebellar atrophy in MERRF.