Research underscores importance of both genetic and functional testing in diagnosing mitochondrial disorders, particularly for cases with low-heteroplasmy deletions that otherwise could go undetected

HOUSTON, March 21, 2025 (GLOBE NEWSWIRE) -- Baylor Genetics, a clinical diagnostic laboratory celebrating a decade at the forefront of genetic testing, today shared research on the value of both genetic and functional testing in diagnosing mitochondrial disorders at the 2025 ACMG Annual Clinical Genetics Meeting, in Los Angeles, CA. The session, titled Detecting Mitochondrial Electron Transport Chain Enzyme Defects in Low-Heteroplasmy Single Large-Scale mtDNA Deletion Syndromes (SLSMDSs), was presented by Xueyang Pan, PhD, clinical biochemical genetics fellow at Baylor Genetics.

A retrospective review was conducted of 1,118 clinical cases where electron transport chain (ETC) functional testing and mtDNA (mitochondrial DNA) genome sequencing were performed on muscle samples. The focus of the study is on low-heteroplasmy single large-scale mtDNA deletions (SLSMD) – where only a small percentage of the mtDNA within a cell carry the deletion – making them difficult to detect and interpret. This research explores how functional changes in muscle can arise from mtDNA deletions and demonstrates the capability of long-range PCR testing plus NGS testing to successfully detect low-heteroplasmy mtDNA deletions.

“The new data underscores the importance of comprehensive molecular testing and functional evaluations in diagnosing mtDNA deletion syndrome,” said Christine Eng, M.D., Chief Medical Officer and Chief Quality Officer at Baylor Genetics. “Our findings reveal that even low-level mtDNA deletions can significantly impact mitochondrial function, challenging traditional assumptions about disease severity thresholds. These insights pave the way for improved diagnostic accuracy and a better understanding of the genotype-phenotype relationship in mitochondrial disorders.”

Key Takeaways

• Effective Detection: Long-range PCR combined with NGS is effective in detecting low-heteroplasmy mtDNA deletions.
• Functional Confirmation: ETC studies can confirm mitochondrial dysfunction even when heteroplasmy levels are low.
• Pathogenicity of Low-Level Deletions: Mitochondrial dysfunction can occur with heteroplasmy levels well below thresholds expected to cause mitochondrial disorders.
• Complete Evaluation is Critical: Comprehensive molecular and functional evaluations are critical for understanding the clinical impact of SLSMDs.

Learn more about the study by clicking here. Baylor Genetics is currently exhibiting at ACMG and can be found at Booth #217.

About Baylor Genetics 
As a pioneer of precision medicine for over 45 years, Baylor Genetics is a leading diagnostic genomics partner offering a full spectrum of clinically relevant genetic testing, including Whole Genome Sequencing, Whole Exome Sequencing, and focused panels. Through a joint venture of H.U. Group Holdings, Inc. and Baylor College of Medicine, Baylor Genetics combines rapid and comprehensive precision diagnostics options with the support of genetic counselors to help clinicians avoid a lengthy diagnostic odyssey for their patients, guide medical management, and ensure no patient with a genetic disorder gets left behind. Baylor Genetics’ testing menu covers family planning, pregnancy, neonatal and pediatric testing, oncology, and many other specialized testing options. Located in Houston’s Texas Medical Center, Baylor Genetics serves clients in 50 states and 16 countries. Learn more about what’s next.

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