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Targeted exome sequencing for mitochondrial disorders reveals high genetic heterogeneity

Jeana T DaRe1, Valeria Vasta2, John Penn2, Nguyen-Thao B Tran2 and Si Houn Hahn23*

  • * Corresponding author: Si H Hahn

  • † Equal contributors

Author Affiliations

1 Transgenomic, Inc, 5 Science Park, New Haven, CT 06511, USA

2 Seattle Children’s Hospital Research Institute, 1900 9th Ave, Seattle, WA 98101, USA

3 Department of Pediatrics, Division of Genetic Medicine, University of Washington, School of Medicine/Seattle Children’s Hospital, 4800 Sand Point Way, Seattle, WA 98105, USA

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BMC Medical Genetics 2013, 14:118  doi:10.1186/1471-2350-14-118

Published: 11 November 2013



Mitochondrial disorders are difficult to diagnose due to extreme genetic and phenotypic heterogeneities.


We explored the utility of targeted next-generation sequencing for the diagnosis of mitochondrial disorders in 148 patients submitted for clinical testing. A panel of 447 nuclear genes encoding mitochondrial respiratory chain complexes, and other genes inducing secondary mitochondrial dysfunction or that cause diseases which mimic mitochondrial disorders were tested.


We identified variants considered to be possibly disease-causing based on family segregation data and/or variants already known to cause disease in twelve genes in thirteen patients. Rare or novel variants of unknown significance were identified in 45 additional genes for various metabolic, genetic or neurogenetic disorders.


Primary mitochondrial defects were confirmed only in four patients indicating that majority of patients with suspected mitochondrial disorders are presumably not the result of direct impairment of energy production. Our results support that clinical and routine laboratory ascertainment for mitochondrial disorders are challenging due to significant overlapping non-specific clinical symptoms and lack of specific biomarkers. While next-generation sequencing shows promise for diagnosing suspected mitochondrial disorders, the challenges remain as the underlying genetic heterogeneity may be greater than suspected and it is further confounded by the similarity of symptoms with other conditions as we report here.

Mitochondrial disorder; Respiratory chain complexes; Electron transport chains; Next-generation sequencing; Targeted exome