Most patients with mutations in the tRNA(lys) gene (MTTK) present with symptoms from the central nervous system (CNS). We describe a 41-year-old woman with pure myopathy associated with a novel de novo mtDNA mutation, mt.8340G>A, which was heteroplasmic in muscle (53%), blood, urine and mouth epithelial cells (<7%). No other family members, including her mother, carried the mutation. She presented with exercise intolerance from age 9, and since age 20 she experienced ptosis and reduced ocular motility. A muscle biopsy revealed ragged red fibres (10%), no COX negative fibres, and many fibres with central nuclei (30%), indicating ongoing damage and repair. The present case expands the mutational and phenotypic spectrum of diseases associated with mutations in MTTK.
Neuromuscular Disorders, 2014, Vol 24, Issue 2, p. 162-166
Adult; Base Sequence; DNA Contamination; DNA, Mitochondrial; Female; Humans; Molecular Sequence Data; Muscle, Skeletal; Muscular Diseases; Pedigree; Point Mutation; RNA, Transfer, Lys; Case Reports; Journal Article