Progressive external ophthalmoplegia due to a recurrent de novo m.15990C > T MT-TP (mt-tRNA(Pro)) gene variant

Joshi, Pushpa Raj; Baty, Karen; Hopton, Sila; Cordts, Isabell; Falkous, Gavin; Schoser, Benedikt; Blakely, Emma L.; Taylor, Robert W. und Deschauer, Marcus (2020): Progressive external ophthalmoplegia due to a recurrent de novo m.15990C > T MT-TP (mt-tRNA(Pro)) gene variant. In: Neuromuscular Disorders, Bd. 30, Nr. 4: S. 346-350

Abstract

Progressive external ophthalmoplegia is typically associated with single or multiple mtDNA deletions but occasionally mtDNA single nucleotide variants within mitochondrial transfer RNAs (mt-tRNAs) are identified. We report a 34-year-old female sporadic patient with progressive external ophthalmoplegia accompanied by exercise intolerance but neither fixed weakness nor multisystemic involvement. Histopathologically, abundant COX-deficient fibres were present in muscle with immunofluorescence analysis confirming the loss of mitochondrial complex I and IV proteins. Molecular genetic analysis identified a rare heteroplasmic m.15990C >T mt-tRNA(Pro) variant reported previously in a single patient with childhood-onset myopathy. The variant in our patient was restricted to muscle. Single muscle fibre analysis identified higher heteroplasmy load in COX-deficient fibres than COX-normal fibres, confirming segregation of high heteroplasmic load with a biochemical defect. Our case highlights the phenotypic variability typically observed with pathogenic mt-tRNA mutations, whilst the identification of a second case with the m.15990C >T mutation not only confirms pathogenicity but shows that de novo mt-tRNA point mutations can arise in multiple, unrelated patients. (C) 2020 The Authors. Published by Elsevier B.V.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Medizin
• Themengebiete: 600 Technik, Medizin, angewandte Wissenschaften > 610 Medizin und Gesundheit
• ISSN: 0960-8966
• Sprache: Englisch