Genetic Testing of Mitochondrial Disorders AHS – M2085

Wood et al. (2019) compared the mtDNA sequencing results of the long-read sequencing technology Oxford Nanopore Technologies (ONT) MinION to the Illumina MiSeq, a next generation sequencing platform. A total of 12 patients participated in this study (three healthy controls and nine with known mtDNA deletion disorders). Both of these next-generation sequencing methods were more efficient than LR-PCR and/or Southern Blotting; further, MinION proved to be just as accurate as the Illumina MiSeq in this study, successfully identifying all mtDNA deletions (Wood et al., 2019). This tool may assist in making the mitochondrial disease diagnostic process more efficient and cost effective in the future.

Wagner et al. (2019) researched the effectiveness of exome sequencing (ES) for mitochondrial disease diagnostics; data was used from 2111 clinical cases. The researchers stated that “ES identified known pathogenic mtDNA point mutations in 38 individuals, increasing the diagnostic yield by nearly two percent Analysis of mtDNA variants by ES had a high recall rate (96.2 ± 5.6%) and excellent precision (99.5 ± 2.2%) when compared to the gold standard of targeted mtDNA next generation sequencing” (Wagner et al., 2019). These results suggest that ES should be considered as a diagnostic tool for both nDNA and mtDNA testing.

Legati et al. (2016) suggest a two-tiered approach to genetic testing where targeted NGS is used first in cases of suspected mitochondrial disorders followed by WES in patients who have inconclusive results. “Importantly, WES on selected cases has unraveled the presence of pathogenic mutations in genes encoding non-mitochondrial proteins (e.g. the transcription factor E4F1), an observation that further expands the intricate genetics of mitochondrial disease and suggests a new area of investigation in mitochondrial medicine” (Legati et al., 2016).

Pronicka et al. (2016) suggest that whole-exome sequencing (WES) is a better diagnostic tool than NGS. A total of 113 pediatric Polish patients participated in this study; variants were identified in both nDNA and mtDNA (Pronicka et al., 2016). WES was able to identify “likely causative mutations” in 67 patients, with 50.5% of all detected genetic changes novel variants; further, “In 47 patients, changes in 31 MD-related genes (ACAD9, ADCK3, AIFM1, CLPB, COX10, DLD, EARS2, FBXL4, MTATP6, MTFMT, MTND1, MTND3, MTND5, NAXE, NDUFS6, NDUFS7, NDUFV1, OPA1, PARS2, PC, PDHA1, POLG, RARS2, RRM2B, SCO2, SERAC1, SLC19A3, SLC25A12, TAZ, TMEM126B, VARS2) were identified” (Pronicka et al., 2016).

In a study by Kerr et al. (2020), 390 patients were recruited and tested for mitochondrial disease (MD) through traditional diagnostic pathways (metabolite analysis, tissue neuropathology and respiratory chain enzyme activity) and new diagnostic approaches (next generation sequencing (NGS) and nuclear whole exome sequencing (nWES)). Testing through traditional diagnostic methods resulted in a mitochondrial diagnosis in 115 out of 390 patients (29.50%). In comparison, 116 out of 390 patients were recruited for NGS, which identified 36 patients (31%) with a mitochondrial diagnosis. To confirm diagnosis, patients were further tested through nWES, which provided a secondary diagnosis in “two cases who already had a pathogenic variant in mtDNA, and a revised diagnosis (GLUL) in one case that had abnormal pathology but no pathogenic mtDNA variant” (Kerr et al., 2020). nWES also identified a mitochondrial diagnosis in one patient who tested negative from NGS. The author offers a diagnostic evaluation strategy, as shown in the figure below, and recommends that “a non-invasive, bigenomic sequencing (BGS) approach (using both a nWES and optimized mtDNA analysis to include large deletions) should be the first step in investigating for mitochondrial diseases. There may still be a role for tissue biopsy in unsolved cases or when the diagnosis is still not clear after NGS studies” (Kerr et al., 2020).

Another study clearly demonstrates the heterogeneity of genetic mutations causing mitocho ndrial disorders. Of the 142 patients with childhood-onset mitochondrial disorders, researchers “identified 37 novel mutations in known mitochondrial disease genes and three mitochondriarelated genes (MRPS23, QRSL1, and PNPLA4) as novel causative genes” (Kohda et al., 2016). These researchers utilized whole mtDNA and exome and chromosomal aberration analysis approaches to “enhance the ability to identify pathogenic gene mutations in patients” (Kohda et al., 2016).

A study by Fang et al. (2017) recruited 141 children with suspected mitochondrial disorders and used NGS to identify genetic characteristics. Forty children were gene confirmed with a known mitochondrial disease; 62.5% of those cases were due to a mtDNA mutation and 37.5% due to a nDNA mutation. This study found the most prevalent disorders to be Leigh Syndrome and MELAS (Fang et al., 2017).

Spath et al. (2021) studied parallel preimplantation genetic testing (PGT) for mtDNA disease and aneuploidy on four patients at risk of transmitting mtDNA disease. Aneuploidy is the condition of having an abnormal number of chromosomes. “Half of the embryos tested were shown to be aneuploid (16/33).” Notably, not all the participants had the same mtDNA mutations. Patients A and D had a m.8993T>G mutation; mutations were detected in embryo biopsies from Patient A but not Patient B. Patient C had a m.10191T.G mutation, no mutations were detected in embryo biopsies from Patient C. Patient D had a m3243A>G mutation, mutations were detected in embryo biopsies from Patient D. Patients A and D displayed somatic heteroplasmy for mtDNA mutations, “heteroplasmic women had a higher incidence of affected embryos than those with undetectable somatic mutant mtDNA but were still able to produce mutation-free embryos.” The authors concluded that “strategies providing a combination of PGT for mtDNA disease and aneuploidy may be advantageous compared with approaches that consider only mtDNA” (Spath et al., 2021).

Wu et al. (2021) evaluated the cost-efficiency and cost-benefit of genomic sequencing for children presenting clinical indications of mitochondrial diseases compared to the conventional diagnosis pathway in Australia. The authors used a decision tree model approach and a discrete-event simulation approach on data from 78 pediatric-onset patients. The conventional diagnosis pathway refers to a diagnostic workup including metabolic, imaging, and histopathological investigations, and genetic testing. Genomic sequencing was less costly and more effective than conventional care. The authors concluded that “genomic sequencing is cost-saving relative to traditional investigative approaches, while enabling more diagnoses to be made in a timely manner, offering substantial personal benefits to children and their families” (Wu et al., 2021).

Farahvash et al. (2021) did a case study on two siblings with mitochondrial neurogastrointestinal encephalopathy disease (MNGIE). The two patients experienced gastrointestinal and cachexia symptoms for years and underwent numerous exploratory tests and surgeries which did not improve their condition. Eventually, the patients were diagnosed with MNGIE following genetic testing for the TYMP gene. The authors concluded that “MNGIE diagnosis is important to establish to avoid unnecessary invasive testing for gastrointestinal, ophthalmological, and neurological symptoms and to ensure patients receive appropriate nutritional and genetic counselling” (Farahvash et al., 2021).

Guidelines and Recommendations

Mitochondrial Medicine Society

The Mitochondrial Medicine Society published the following consensus recommendations on genetic testing for mitochondrial disorders (Parikh et al., 2015):

1. “Massively parallel sequencing/NGS of the mtDNA genome is the preferred methodology when testing mtDNA and should be performed in cases of suspected mitochondrial disease instead of testing for a limited number of pathogenic point mutations.
2. Patients with a strong likelihood of mitochondrial disease because of a mtDNA mutation and negative testing in blood, should have mtDNA assessed in another tissue to avoid the possibility of missing tissue-specific mutations or low levels of heteroplasmy in blood; tissue-based testing also helps assess the risk of other organ involvement and heterogeneity in family members and to guide genetic counseling.
3. Heteroplasmy analysis in urine can selectively be more informative and accurate than testing in blood alone, especially in cases of MELAS due to the common m. 3243A>G mutation.
4. mtDNA deletion and duplication testing should be performed in cases of suspected mitochondrial disease via NGS of the mtDNA genome, especially in all patients undergoing a diagnostic tissue biopsy.
   1. If a single small deletion is identified using polymerase chain reaction– based analysis, then one should be cautious in associating these findings with a primary mitochondrial disorder.
   2. When multiple mtDNA deletions are noted, sequencing of nuclear genes involved in mtDNA biosynthesis is recommended.
5. When a tissue specimen is obtained for mitochondrial studies, mtDNA content (copy number) testing via real-time quantitative polymerase chain reaction should strongly be considered for mtDNA depletion analysis because mtDNA depletion may not be detected in blood.
   1. mtDNA proliferation is a nonspecific compensatory finding that can be seen in primary mitochondrial disease, secondary mitochondrial dysfunction, myopathy, hypotonia, and as a by-product of regular, intense exercise.
6. When considering nuclear gene testing in patients with likely primary mitochondrial disease, NGS methodologies providing complete coverage of known mitochondrial disease genes is preferred. Single-gene testing should usually be avoided because mutations in different genes can produce the same phenotype. If no known mutation is identified via known NGS gene panels, then whole exome sequencing should be considered.”

The Mitochondrial Medicine Society also commented on the set of mtDNA depletion syndromes, which are “characterized by a significant reduction in mtDNA copy number in affected tissues”. They note that diagnosis of these conditions “requires quantification of mtDNA content, typically in affected tissue, with identification of a significant decrease below the mean of normal age, gender, and tissue-specific control when normalized to nDNA tissue content”. Since NGS of the mtDNA genome does not identify mtDNA content, a separate quantitative real-time polymerase chain reaction must be used (Parikh et al., 2015).

The Mitochondrial Medicine Society in 2017 released their guidelines regarding patient care standards. Within this set of guidelines, they state, “Pregnancy in mitochondrial disease also elicits the concern of transmission of a genetic disorder. Appropriate preconception genetic counseling and discussion of options of prenatal testing are needed. A fetus affected by mitochondrial disease may also be at higher risk for prenatal morbidity. Finally, premature ovarian failure is a feature of several mitochondrial disorders and affected women should be referred for assisted reproductive technologies if they wish to have children” (Parikh et al., 2017).

Association for Clinical Genomic Science (ACGS)

The ACGS published guidelines for the genetic testing strategies for diagnostic and familial testing, variant interpretation and reporting, and prenatal diagnosis and reproductive options. The guidelines report the minimal level of testing recommended for the most common diagnostic referrals, listed below, noting possible further testing with nuclear DNA testing and whole mtDNA sequencing for all phenotypes.

• Phenotype: ataxia, possible diagnosis of late-childhood or adult-onset peripheral neuropathy, pigmentary retinopathy (NARP) or mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Minimum level of testing for: m.8993T>G p.(Leu156Arg), m.8993T>C p.(Leu156Pro)(MT-ATP6), m.3243A>G (MT-TL1).
• Phenotype: cardiomyopathy, familial hypertrophic cardiomyopathy with maternal inheritance. Minimum level of testing for: m.4300A>G (MT-TI), m.3243A>G (MTTL1)
• Phenotype: diabetes mellitus and sensorineural hearing loss. Minimum level of testing for: m.3243A>G (MT-TL1), m.3243A>G (MT-TL1).
• Phenotype: encephalopathy/seizures with lactic acidosis, possible diagnosis of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) or infantile onset subacute relapsing encephalopathy, cerebellar and brain stem signs (MILS). Minimum level of testing for: m.3243A>G, (MT-TL1), m.8993T>G p.(Leu156Arg), m.8993T>C p.(Leu156Pro), (MT-ATP6).
• Phenotype: non-syndromic sensorineural hearing loss, particularly if onset following aminoglycoside exposure. Minimum level of testing for m.1555A>G (MT-RNR1).
• Phenotype: Kearns-Sayre syndrome Onset, below the age of 20 years, PEO and pigmentary retinopathy with one of either cardiac conduction block, cerebrospinal fluid protein concentration greater than 100 mg/dL, or cerebellar ataxia. Minimum level of testing for: large-scale mtDNA rearrangements (single and multiple deletions), m.3243A>G (MT-TL1).
• Phenotype: Leber hereditary optic neuropathy, optic atrophy, childhood or midlife (adult onset) acute or subacute painless bilateral central vision loss. Minimum level of testing for: m.3460G>A p.(Ala52Thr) (MT-ND1), m.11778G>A p.(Arg340His) (MT-ND4), m.14484T>C p.(Met64Val) (MT-ND6).
• Phenotype: mtDNA depletion syndrome, neonatal or infantile hepatocerebral, myopathic, encephalomyopathic or neurogastrointestinal presentations; may also include growth failure, lactic acidosis, and hypoglycemia. Minimum level of testing for: mtDNA copy number analysis.
• Phenotype: myoclonic epilepsy, myoclonus, seizures; cerebellar ataxia; myopathy. Minimum level of testing for: m.8344A>G (MT-TK), m.3243A>G (MT-TL1).
• Phenotype: Pearson syndrome, sideroblastic anemia of childhood; Pancytopenia; Exocrine pancreatic failure. Minimum level of testing for: large-scale mtDNA rearrangements.
• Phenotype: progressive external ophthalmoplegia (PEO), ptosis, typically adult-onset ptosis, paralysis of the extraocular muscles (ophthalmoplegia), oropharyngeal weakness, and variably severe proximal limb weakness. Minimum level of testing for: large-scale mtDNA rearrangements (single and multiple deletions, m.3243A>G (MTTL1).
• Phenotype: stroke-like episodes, typically before age 40 years. Minimum level of testing for: m.3243A>G (MT-TL1) (Mavraki et al., 2020).

European Academy of Neurology (EAN)

Regarding genetic testing for mitochondrial encephalopathy, lactic acidosis and stroke‐like episodes (MELAS), the EAN recommends “Urgent genetic testing for MELAS should be considered in patients presenting with suspected SLE [stroke‐like episode]. Search for the m.3243A>G variant (in urine where possible) and, if m.3243A>G variant is negative, POLG sequencing is required. Muscle biopsy should be considered after excluding m.3243A>G and POLG variants.” The EAN also notes that valproic acid is “contraindicated, mainly in patients with POLG variants” (Mancuso et al., 2020).

MNGIE International Network

The MNGIE [Mitochondrial neurogastrointestinal encephalomyopathy] International Network recommended TYMP sequencing to confirm a MNGIE diagnosis. If a variant of unknown significance or a wild-type variant is found, the Network recommends biochemical testing of thymidine (dThd) and deoxyuridine levels to determine thymidine phosphorylase (TP) activity. The Network also remarks on several treatment options (both short- and long-term), which focus on restoring the biochemical balance of the patient (Hirano et al., 2020).

State and Federal Regulations, as applicable

Food and Drug Administration (FDA)

Many labs have developed specific tests that they must validate and perform in house. These laboratory-developed tests (LDTs) are regulated by the Centers for Medicare and Medicaid (CMS) as high-complexity tests under the Clinical Laboratory Improvement Amendments of 1988 (CLIA ’88). LDTs are not approved or cleared by the U. S. Food and Drug Administration; however, FDA clearance or approval is not currently required for clinical use.

Billing/Coding/Physician Documentation Information

This policy may apply to the following codes. Inclusion of a code in this section does not guarantee that it will be reimbursed. For further information on reimbursement guidelines, please see Administrative Policies on the Blue Cross Blue Shield of North Carolina web site at www.bcbsnc.com. They are listed in the Category Search on the Medical Policy search page.

Applicable service codes: 81401, 81403, 81404, 81405, 81406, 81440, 81460, 81465, 81479, 0212U, 0213U, 0214U, 0215U, 0417U

BCBSNC may request medical records for determination of medical necessity. When medical records are requested, letters of support and/or explanation are often useful, but are not sufficient documentation unless all specific information needed to make a medical necessity determination is included. 

Scientific Background and Reference Sources

Akesson, L., Eggers, S., Chong, B., Hunter, M., Krzesinski, E., Brown, N., Tan, T. Y., Richmond, C., Thorburn, D., Christodoulou, J., Stark, Z., & Lunke, S. (2019). Rapid mitochondrial genome (MTDNA) sequencing: facilitating rapid diagnosis of mitochondrial diseases in paediatric acute care. 51, 118–S119. https://doi.org/10.1016/j.pathol.2018.12.339

ARUP. (2023). Mitochondrial Disorders Panel (mtDNA and Nuclear Genes). ARUP Laboratories. https://ltd.aruplab.com/Tests/Pub/3001959

Barca, E., Long, Y., Cooley, V., Schoenaker, R., Emmanuele, V., DiMauro, S., Cohen, B. H., Karaa, A., Vladutiu, G. D., Haas, R., Van Hove, J. L. K., Scaglia, F., Parikh, S., Bedoyan, J. K., DeBrosse, S. D., Gavrilova, R. H., Saneto, R. P., Enns, G. M., Stacpoole, P. W., . . . Hirano, M. (2020). Mitochondrial diseases in North America: An analysis of the NAMDC Registry. Neurol Genet, 6(2), e402. https://doi.org/10.1212/nxg.0000000000000402

Baylor. (2023). Providing insights into unclear health conditions through Mitochondrial testing. Baylor Genetics https://www.baylorgenetics.com/mitochondrial/

Chinnery, P. F. (2014). Mitochondrial Disorders Overview. In M. P. Adam, H. H. Ardinger, R. A. Pagon, S. E. Wallace, L. J. H. Bean, K. Stephens, & A. Amemiya (Eds.), GeneReviews((R)) (Vol. 2014 update). University of Washington, Seattle. https://www.ncbi.nlm.nih.gov/books/NBK1224/

Darin, N., Oldfors, A., Moslemi, A. R., Holme, E., & Tulinius, M. (2001). The incidence of mitochondrial encephalomyopathies in childhood: clinical features and morphological, biochemical, and DNA abnormalities. Ann Neurol, 49(3), 377-383. https://pubmed.ncbi.nlm.nih.gov/11261513/

Dimmock, D. P., & Lawlor, M. W. (2017). Presentation and Diagnostic Evaluation of Mitochondrial Disease. Pediatr Clin North Am, 64(1), 161-171. https://doi.org/10.1016/j.pcl.2016.08.011

Fang, F., Liu, Z., Fang, H., Wu, J., Shen, D., Sun, S., Ding, C., Han, T., Wu, Y., Lv, J., Yang, L., Li, S., Lv, J., & Shen, Y. (2017). The clinical and genetic characteristics in children with mitochondrial disease in China. Sci China Life Sci, 60(7), 746-757. https://doi.org/10.1007/s11427- 017-9080-y

Farahvash, A., Kassardjian, C. D., & Micieli, J. A. (2021). Mitochondrial Neurogastrointestinal Encephalopathy Disease: A Rare Disease Diagnosed in Siblings with Double Vision. Case Rep Ophthalmol, 12(1), 174-181. https://doi.org/10.1159/000514098

GeneDX. (2023a). Combined Mito Genome Plus Mito Focused Nuclear Gene Panel.

GeneDx, Inc. https://www.genedx.com/tests/detail/combined-mito-genome-plus-mito-focused-nuclear-genepanel-736 GeneDX. (2023b, August 2021). MitoXpanded Panel. GeneDx, Inc. https://providers.genedx.com/tests/detail/mitoxpanded-panel-891

Gorman, G. S., Schaefer, A. M., Ng, Y., Gomez, N., Blakely, E. L., Alston, C. L., Feeney, C., Horvath, R., Yu-Wai-Man, P., Chinnery, P. F., Taylor, R. W., Turnbull, D. M., & McFarland, R. (2015). Prevalence of nuclear and mitochondrial DNA mutations related to adult mitochondrial disease. Ann Neurol, 77(5), 753-759. https://doi.org/10.1002/ana.24362

Hatakeyama, H., & Goto, Y. (2016). Concise Review: Heteroplasmic Mitochondrial DNA Mutations and Mitochondrial Diseases: Toward iPSC-Based Disease Modeling, Drug Discovery, and Regenerative Therapeutics. Stem Cells, 34(4), 801-808. https://doi.org/10.1002/stem.2292

Hirano, M., Carelli, V., De Giorgio, R., Pironi, L., Accarino, A., Cenacchi, G., D'Alessandro, R., Filosto, M., Martí, R., Nonino, F., Pinna, A. D., Baldin, E., Bax, B. E., Bolletta, A., Bolletta, R., Boschetti, E., Cescon, M., D'Angelo, R., Dotti, M. T., . . . Zeviani, M. (2020). Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE): Position paper on diagnosis, prognosis, and treatment by the MNGIE International Network. J Inherit Metab Dis. https://doi.org/10.1002/jimd.12300

Horvath, R., & Chinnery, P. (2019). Diagnostic Approach to Mitochondrial Diseases. https://doi.org/10.1007/978-3-030-05517-2_17

Kerr, M., Hume, S., Omar, F., Koo, D., Barnes, H., Khan, M., Aman, S., Wei, X.-C., Alfuhaid, H., McDonald, R., McDonald, L., Newell, C., Sparkes, R., Hittel, D., & Khan, A. (2020). MITOFIND: A study in 390 patients to determine a diagnostic strategy for mitochondrial disease. Molecular Genetics and Metabolism. https://doi.org/10.1016/j.ymgme.2020.08.009

Kohda, M., Tokuzawa, Y., Kishita, Y., Nyuzuki, H., Moriyama, Y., Mizuno, Y., Hirata, T., Yatsuka, Y., Yamashita-Sugahara, Y., Nakachi, Y., Kato, H., Okuda, A., Tamaru, S., Borna, N. N., Banshoya, K., Aigaki, T., Sato-Miyata, Y., Ohnuma, K., Suzuki, T., . . . Okazaki, Y. (2016). A Comprehensive Genomic Analysis Reveals the Genetic Landscape of Mitochondrial Respiratory Chain Complex Deficiencies. PLoS Genet, 12(1), e1005679. https://doi.org/10.1371/journal.pgen.1005679

Legati, A., Reyes, A., Nasca, A., Invernizzi, F., Lamantea, E., Tiranti, V., Garavaglia, B., Lamperti, C., Ardissone, A., Moroni, I., Robinson, A., Ghezzi, D., & Zeviani, M. (2016). New genes and pathomechanisms in mitochondrial disorders unraveled by NGS technologies. Biochim Biophys Acta, 1857(8), 1326-1335. https://doi.org/10.1016/j.bbabio.2016.02.022

Lightowlers, R. N., Taylor, R. W., & Turnbull, D. M. (2015). Mutations causing mitochondrial disease: What is new and what challenges remain? Science, 349(6255), 1494-1499. https://doi.org/10.1126/science.aac7516

Ling, T.-k., Law, C.-y., Ko, C.-h., Fong, N.-c., Wong, K.-c., Lee, K.-l., Chiu-wing Chu, W., BreaCalvo, G., & Lam, C.-w. (2019). A common COQ4 mutation in undiagnosed mitochondrial disease: a local case series. 51, S112–S113. https://doi.org/10.1016/j.pathol.2018.12.317

Mancuso, M., Arnold, M., Bersano, A., Burlina, A., Chabriat, H., Debette, S., Enzinger, C., Federico, A., Filla, A., Finsterer, J., Hunt, D., Lesnik Oberstein, S., Tournier-Lasserve, E., & Markus, H. S. (2020). Monogenic cerebral small-vessel diseases: diagnosis and therapy. Consensus recommendations of the European Academy of Neurology. Eur J Neurol, 27(6), 909-927. https://doi.org/10.1111/ene.14183

Mascialino, B., Leinonen, M., & Meier, T. (2012). Meta-analysis of the prevalence of Leber hereditary optic neuropathy mtDNA mutations in Europe. Eur J Ophthalmol, 22(3), 461-465. https://doi.org/10.5301/ejo.5000055

Mavraki, E., Labrum, R., Sergeant, K., Alston, C., Woodward, C., Smith, C., Watson, E. L., Polke, J., Taylor, R. W., & Fratter, C. (2020). Best Practice Guidelines for the Molecular Diagnosis of Mitochondrial Disease. https://www.acgs.uk.com/media/11935/bpg-for-the-molecular-diagnosisof-mitochondrial-disease_ratified-november-2020.pdf

McCormick, E. M., Zolkipli-Cunningham, Z., & Falk, M. J. (2018). Mitochondrial disease genetics update: recent insights into the molecular diagnosis and expanding phenotype of primary mitochondrial disease. Curr Opin Pediatr, 30(6), 714-724. https://doi.org/10.1097/mop.0000000000000686

Medical Neurogenetics, L. (2022). Mitochondrial Genome Sequencing + Deletion Analysis. Medical Neurogenetics, LLC. https://mnglabs.labcorp.com/tests/MOL189/mitochondrial-genomesequencing-deletion-analysis

Meyers, D. E., Basha, H. I., & Koenig, M. K. (2013). Mitochondrial cardiomyopathy: pathophysiology, diagnosis, and management. Tex Heart Inst J, 40(4), 385-394. https://pubmed.ncbi.nlm.nih.gov/24082366/

Ng, Y. S., Alston, C. L., Diodato, D., Morris, A. A., Ulrick, N., Kmoch, S., Houstek, J., Martinelli, D., Haghighi, A., Atiq, M., Gamero, M. A., Garcia-Martinez, E., Kratochvilova, H., Santra, S., Brown, R. M., Brown, G. K., Ragge, N., Monavari, A., Pysden, K., . . . McFarland, R. (2016). The clinical, biochemical and genetic features associated with RMND1-related mitochondrial disease. J Med Genet, 53(11), 768-775. https://doi.org/10.1136/jmedgenet-2016-103910

O'Brien, M., Cryan, J., Brett, F., Howley, R., & Farrell, M. (2014). Ten years on: genetic screening for mitochondrial disease in Ireland. Clin Neuropathol, 33(4), 279-283. https://doi.org/10.5414/np300722

O'Ferrall, E. (2022). Mitochondrial myopathies: Clinical features and diagnosis. Wolters Kluwer. https://www.uptodate.com/contents/mitochondrial-myopathies-clinical-features-and-diagnosis

Parikh, S., Goldstein, A., Karaa, A., Koenig, M. K., Anselm, I., Brunel-Guitton, C., Christodoulou, J., Cohen, B. H., Dimmock, D., Enns, G. M., Falk, M. J., Feigenbaum, A., Frye, R. E., Ganesh, J., Griesemer, D., Haas, R., Horvath, R., Korson, M., Kruer, M. C., . . . Chinnery, P. F. (2017). Patient care standards for primary mitochondrial disease: a consensus statement from the Mitochondrial Medicine Society. Genet Med, 19(12). https://doi.org/10.1038/gim.2017.107

Parikh, S., Goldstein, A., Koenig, M. K., Scaglia, F., Enns, G. M., Saneto, R., Anselm, I., Cohen, B. H., Falk, M. J., Greene, C., Gropman, A. L., Haas, R., Hirano, M., Morgan, P., Sims, K., Tarnopolsky, M., Van Hove, J. L., Wolfe, L., & DiMauro, S. (2015). Diagnosis and management of mitochondrial disease: a consensus statement from the Mitochondrial Medicine Society. Genet Med, 17(9), 689-701. https://doi.org/10.1038/gim.2014.177

Pronicka, E., Piekutowska-Abramczuk, D., Ciara, E., Trubicka, J., Rokicki, D., KarkucinskaWieckowska, A., Pajdowska, M., Jurkiewicz, E., Halat, P., Kosinska, J., Pollak, A., Rydzanicz, M., Stawinski, P., Pronicki, M., Krajewska-Walasek, M., & Ploski, R. (2016). New perspective in diagnostics of mitochondrial disorders: two years' experience with whole-exome sequencing at a national paediatric centre. J Transl Med, 14(1), 174. https://doi.org/10.1186/s12967-016-0930-9

Schon, E. A., DiMauro, S., & Hirano, M. (2012). Human mitochondrial DNA: roles of inherited and somatic mutations. Nat Rev Genet, 13(12), 878-890. https://doi.org/10.1038/nrg3275

Skladal, D., Halliday, J., & Thorburn, D. R. (2003). Minimum birth prevalence of mitochondrial respiratory chain disorders in children. Brain, 126(Pt 8), 1905-1912. https://doi.org/10.1093/brain/awg170

Sofou, K., de Coo, I. F. M., Ostergaard, E., Isohanni, P., Naess, K., De Meirleir, L., Tzoulis, C., Uusimaa, J., Lonnqvist, T., Bindoff, L. A., Tulinius, M., & Darin, N. (2018). Phenotype-genotype correlations in Leigh syndrome: new insights from a multicentre study of 96 patients. J Med Genet, 55(1), 21-27. https://doi.org/10.1136/jmedgenet-2017-104891

Spath, K., Babariya, D., Konstantinidis, M., Lowndes, J., Child, T., Grifo, J. A., Poulton, J., & Wells, D. (2021). Clinical application of sequencing-based methods for parallel preimplantation genetic testing for mitochondrial DNA disease and aneuploidy. Fertil Steril, 115(6), 1521-1532. https://doi.org/10.1016/j.fertnstert.2021.01.026

Taylor, R. W., Pyle, A., Griffin, H., Blakely, E. L., Duff, J., He, L., Smertenko, T., Alston, C. L., Neeve, V. C., Best, A., Yarham, J. W., Kirschner, J., Schara, U., Talim, B., Topaloglu, H., Baric, I., Holinski-Feder, E., Abicht, A., Czermin, B., . . . Chinnery, P. F. (2014). Use of whole-exome sequencing to determine the genetic basis of multiple mitochondrial respiratory chain complex deficiencies. Jama, 312(1), 68-77. https://doi.org/10.1001/jama.2014.7184

Thompson, K., Collier, J., Glasglow, R., Robertson, F., Pyle, A., Blakely, E., Alston, C., Olahova, M., McFarland, R., & Taylor, R. W. (2019). Recent advances in understanding the molecular genetic basis of mitochondrial disease. https://doi.org/10.1002/jimd.12104

Variantyx. (2023a). Genomic Unity® Exome Plus Analysis. https://www.variantyx.com/productsservices/rare-disorder-genetics/comprehensive-analyses/genomic-unity-exome-plus-analysis/ Variantyx. (2023b). Genomic Unity® Whole Genome Analysis. https://www.variantyx.com/products-services/rare-disorder-genetics/comprehensiveanalyses/genomic-unity-whole-genome-analysis/

Wagner, M., Berutti, R., Lorenz-Depiereux, B., Graf, E., Eckstein, G., Mayr, J. A., Meitinger, T., Ahting, U., Prokisch, H., Strom, T. M., & Wortmann, S. B. (2019). Mitochondrial DNA mutation analysis from exome sequencing-A more holistic approach in diagnostics of suspected mitochondrial disease. J Inherit Metab Dis, 42(5), 909-917. https://doi.org/10.1002/jimd.12109

Wood, E., Parker, M., Dunning, M., Hesketh, S., Wang, D., Pink, R., & Fratter, C. (2019). Clinical long-read sequencing of the human mitochondrial genome for mitochondrial disease diagnostics. https://doi.org/10.1101/597187

Wu, Y., Balasubramaniam, S., Rius, R., Thorburn, D. R., Christodoulou, J., & Goranitis, I. (2021). Genomic sequencing for the diagnosis of childhood mitochondrial disorders: a health economic evaluation. Eur J Hum Genet. https://doi.org/10.1038/s41431-021-00916-8

Specialty Matched Consultant Advisory Panel review 3/2020

Medical Director review 3/2020

Specialty Matched Consultant Advisory Panel review 3/2021

Medical Director review 3/2021

Medical Director review 1/2022

Medical Director review 1/2023

Medical Director review 1/2024

Policy Implementation/Update Information

1/1/2019 New policy developed. BCBSNC will provide coverage for genetic testing of mitochondrial disorders when it is determined to be medically necessary because criteria and guidelines are met. Medical Director review 1/1/2019. Policy noticed 1/1/2019 for effective date 4/1/2019. (jd)

4/16/2019 Description section and policy guidelines updated. When Covered section revised for clarity and removed criteria concerning prenatal testing as this is addressed in a separate policy. Policy intent unchanged. Added 96040 and S0265 for genetic counseling which was added as item #3 under the When Covered section. Medical Director review 4/2019(jd)

2/11/20 Annual review by Avalon 4th Quarter 2019 CAB. No revisions and no change to policy intent. Medical Director review 12/2019. (jd)

4/14/20 Specialty Matched Consultant Advisory Panel review 3/2020. Medical Director review 3/2020. (jd)

2/9/21 Annual review by Avalon 4th Quarter 2020 CAB. Related Policies added to description section. Item #3 added as follows to the When Covered section: “Quantification of mtDNA in tissue to diagnose mtDNA depletion syndrome is considered medically necessary.” The following statements were added to the When Not Covered section as follows: “Combination testing of mitochondrial genome testing with WES with intronic variants testing and regulatory variants testing, sometimes referred to as whole exome plus testing, including but not limited to Genomic Unity® Exome Plus Analysis is considered not medically necessary.”, and “Combination testing of mitochondrial genome testing with WGS with intronic variants testing and regulatory variants testing, sometimes referred to as Genomic Unity® Whole Genome Analysis is considered not medically necessary.” Policy guidelines and references updated. Removed code box and added codes 0212U-0215U to the Billing/Coding section. Medical Director review 1/2021. (jd)

3/31/21 Specialty Matched Consultant Advisory Panel review 3/2021. Medical Director review 3/2021. (jd)

2/8/22 Reviewed by Avalon 4th Quarter 2021 CAB. Acronyms for MELAS, MERRF, CPEO. mtDNA, WES, and WGS spelled out in both covered and noncovered sections for clarity; no change to policy intent. Description, policy guidelines, and references updated with minor revisions. Medical Director review 1/2022. (jd)

2/7/23 Reviewed by Avalon 4th Quarter 2022 CAB. Description, Policy Guidelines, Billing/Coding and References sections updated, removed Related Policies section. When Covered section edited for clarity, removed criteria "4. Genetic counseling for mitochondrial disorder genetic testing is considered medically necessary." Not Covered section also edited for clarity. Medical Director review 1/2023. (tm)

9/29/23 Added code 0417U to Billing/Coding section for effective date 10/1/23. (tm)

2/21/24 Reviewed by Avalon 4th Quarter 2023 CAB. Description, Policy Guidelines and References sections updated. Related Policies added to Description section. Codes 96040 and S0265 removed from Billing/Coding section. No change to policy statement. Medical Director review 1/2024. (tm)