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Mitochondrial Complex III Deficiency Panel (Nuclear Genes)

Summary and Pricing

Test Method

Exome Sequencing with CNV Detection
Test Code Test Copy Genes Gene CPT Codes Copy CPT Codes
BCS1L 81405,81479
CYC1 81479,81479
LYRM7 81479,81479
TTC19 81479,81479
UQCC2 81479,81479
UQCC3 81479,81479
UQCRB 81479,81479
UQCRC2 81479,81479
UQCRQ 81479,81479
Test Code Test Copy Genes Panel CPT Code Gene CPT Codes Copy CPT Code Base Price
3459Genes x (9)81479 81405(x1), 81479(x17) $990 Order Options and Pricing

Pricing Comments

We are happy to accommodate requests for testing single genes in this panel or a subset of these genes. The price will remain the list price. If desired, free reflex testing to remaining genes on panel is available. Alternatively, a single gene or subset of genes can also be ordered via our Custom Panel tool.

An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.

Click here for costs to reflex to whole PGxome (if original test is on PGxome Sequencing platform).

Click here for costs to reflex to whole PGnome (if original test is on PGnome Sequencing platform).

Turnaround Time

3 weeks on average for standard orders or 2 weeks on average for STAT orders.

Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.

Targeted Testing

For ordering sequencing of targeted known variants, go to our Targeted Variants page.


Genetic Counselors


  • Kym Bliven, PhD

Clinical Features and Genetics

Clinical Features

Mitochondrial complex III (CIII) deficiency is characterized by a deficiency of the third oxidative phosphorylation complex, also referred to as cytochrome bc1 (Fernández-Vizarra and Zeviani 2015). Significant clinical and genetic heterogeneity is observed between affected individuals. Similar to other OXPHOS disorders, recurrent lactic acidosis is a prevalent finding in patients with CIII deficiency, particularly during infections. Additional clinical features may include severe psychomotor delay or impairment, ataxia, muscle weakness, respiratory insufficiency, encephalomyopathy, hypoglycemia, and/or Leigh or Leigh-like syndrome (Fernández-Vizarra and Zeviani 2015; Dallabona et al. 2016; Ardissone et al. 2015). The majority of CIII deficient patients present within the first year of life; however, several individuals with defects in the TTC19 gene presented with an adult-onset disorder initially characterized by psychiatric symptoms (Ardissone et al. 2015).

Pathogenic variants in BCS1L are the most frequent cause of mitochondrial CIII deficiency, and may account for several distinct disease manifestations, including GRACILE syndrome (Growth Retardation, Aminoaciduria, Cholestasis, Iron overload, Lactic acidosis, and Early death) or neonatal proximal tubulopathy and/or liver failure with or without encephalopathy (Fernández-Vizarra and Zeviani 2015). BCS1L-associated CIII deficiency may also present as Björnstad syndrome, a milder disorder characterized by sensorineural hearing loss and pili torti (Hinson et al. 2007).


The mitochondrial respiratory chain complex III (CIII) is composed of 10 nuclear-encoded subunits and one mitochondrial-encoded subunit (MT-CYB), while several additional nuclear-encoded proteins are required for complex assembly (Fernández-Vizarra and Zeviani 2015). The resulting holoenzyme complex plays a critical role in redox-driven proton translocation, which ultimately results in synthesis of adenosine triphosphate (ATP) (Sazanov 2015).

Due to the many structural and accessory subunits required to support the assembly and function of the third complex, mitochondrial CIII deficiency is a genetically heterogeneous disorder. At least 10 genes have been linked to this disease to date. Depending on the cellular localization of the affected gene, this disorder may have an autosomal recessive or maternal mode of inheritance. Causative variants in the nuclear genes (BCS1L, CYC1, LYRM7, TTC19, UQCC2, UQCC3, UQCRB, UQCRC2, and UQCRQ) are inherited in an autosomal recessive manner. In contrast, causative variants in the MT-CYB gene, which is encoded by the mitochondrial genome, are inherited in a maternal manner.

This NextGen Panel covers nine nuclear genes (BCS1L, CYC1, LYRM7, TTC19, UQCC2, UQCC3, UQCRB, UQCRC2, and UQCRQ) that have been associated with mitochondrial complex III deficiency. This panel does not cover MT-CYB.

Please visit individual gene test descriptions for more information regarding each of these genes.

Clinical Sensitivity - Sequencing with CNV PGxome

Many of the genes in this NextGen Panel have only been linked to disease in one or two families to date, making clinical sensitivity difficult to estimate. In one cohort, isolated mitochondrial CIII deficiency accounted for approximately 5% of all oxidative phosphorylation (OXPHOS) disorders (Skladal et al. 2003).

Testing Strategy

This test is performed using Next-Gen sequencing with additional Sanger sequencing as necessary.

This panel provides 100% coverage of all coding exons of the genes plus 10 bases of flanking noncoding DNA in all available transcripts along with other non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as >20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).

One pre-coding variant (c.-147A>G) and one deep intronic variant (c.-50+155T>A) in the BSC1L gene are also covered in this test (Gil-Borlado et al. 2009; Visapää et al. 2002; Lynn et al. 2012).

Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).

Indications for Test

Candidates for this test include patients with a deficiency of mitochondrial complex III, or those who present with symptoms consistent with complex III deficiency.


Official Gene Symbol OMIM ID
BCS1L 603647
CYC1 123980
LYRM7 615831
TTC19 613814
UQCC2 614461
UQCC3 616097
UQCRB 191330
UQCRC2 191329
UQCRQ 612080
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Related Test



  • Ardissone A. et al. 2015. JIMD Reports. 22:115-20. PubMed ID: 25772319
  • Dallabona C. et al. 2016. Brain. 139:782-94. PubMed ID: 26912632
  • Fernández-Vizarra E., Zeviani M. 2015. Frontiers Genetics. 6:134. PubMed ID: 25914718
  • Gil-Borlado M.C. et al. 2009. Mitochondrion. 9:299-305. PubMed ID: 19389488
  • Hinson J.T. et al. 2007. New England Journal of Medicine. 356:809-19. PubMed ID: 17314340
  • Lynn A.M. et al. 2012. Annals of Clinical Biochemistry. 49:201-3. PubMed ID: 22277166
  • Sazanov L.A. 2015. Nature Reviews Molecular and Cellular Biology. 16:375-88. PubMed ID: 25991374
  • Skladal D. et al. 2003. Clinical Pediatrics. 42:703-10. PubMed ID: 14601919
  • Visapää I. et al. 2002. American Journal of Human Genetics. 71:863-76. PubMed ID: 12215968


Ordering Options

We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.

myPrevent - Online Ordering

  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
  • PGnome sequencing panels can be ordered via the myPrevent portal only at this time.

Requisition Form

  • A completed requisition form must accompany all specimens.
  • Billing information along with specimen and shipping instructions are within the requisition form.
  • All testing must be ordered by a qualified healthcare provider.

For Requisition Forms, visit our Forms page

If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.

Specimen Types

Specimen Requirements and Shipping Details

PGxome (Exome) Sequencing Panel

PGnome (Genome) Sequencing Panel

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2) Select Additional Test Options

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Note: acceptable specimen types are whole blood and DNA from whole blood only.
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