A mitochondrial encephalo-myo-neuropathy with a nucleotide position 3271 (T-C) point mutation in the mitochondrial DNA

We report three members of a family, who exhibited a phenotype similar to ' myoclonus epilepsy with ragged-red fibers' but had a genotype usually assoc iated with 'mitochondrial encephalomyopathy with lactic acidosis and stroke -like episodes'. The patients, a 48-year-old female, and her two sons, aged 21 and 19 respectively, presented with photo-reactive syncopal episodes, d isturbances of gait and writing, dysarthria and finger tremor since the 3rd and 2nd decade of life, respectively, that were accompanied also by numbne ss and weakness of the extremities. Subsequently, cerebellar ataxia and myo clonus were also noted. Electromyography revealed both myogenic and neuroge nic muscular changes, and nerve conduction studies demonstrated a sensory-m otor neuropathy. Biopsy showed ragged-red fibers with strongly stained SDH- positive vessels in skeletal muscles, and a marked loss of myelinated fiber s of the sural nerves. Mitochondrial (mt) DNA analyses of peripheral blood. muscles and nerves revealed that all members had a heteroplasmic np3271 (T -C) point mutation in the mitochondrial tRNA-Leu gene (UUR). This family is unique, in that all patients presented with a myoclonus epilepsy with ragg ed-red fibers-like phenotype and had a distinctive peripheral neuropathy, w hile the detected mtDNA 3271 (T-C) mutation has been reported to date only in rare cases of mitochondrial encephalomyopathy with lactic acidosis and s troke-like episodes (C) 2001 Elsevier Science B.V. All rights reserved.