[Mitochondrial respiratory chain diseases. Evaluation and variability in 52 patients].

Introduction: Clinical, electrophysiological, genetic and biochemical deficiencies variability were evaluated in 52 patients diagnosed of mitochondrial respiratory chain diseases (MRCD).

Patients And Methods: 26 men and 26 women, aged 19 to 79 years, were tested by clinical examination, electrophysiological techniques, muscle biopsy and genetic and biochemical studies.

Results: The patients were classified into seven phenotypes: myopathy, chronic progressive external ophthalmoplegia, progressive ophthalmoplegia plus ataxia, Kearns-Sayre syndrome, mitochondrial encephalomyopathy with lactic acidosis and stroke episodes (MELAS), myoclonic encephalopathy with ragged-red fibers (MERRF), and encephalopathies.