Skin Biopsy-Derived Fibroblast Assays Complement Genomic Sequencing in Mitochondrial Disease Diagnosis

Article Impact Level: HIGH
Data Quality: STRONG
Summary of  EMBO Molecular Medicine. https://doi.org/10.1038/s44321-026-00497-3
Dr. Johan L K Van Hove et al.

Points

Childrens Hospital Colorado and University of Colorado researchers systematically evaluated skin biopsy derived fibroblast functional testing across more than thirty international medical centers.
Evaluation of two hundred four primary mitochondrial disease patients demonstrated that combining respiratory chain enzyme assays BN PAGE and assembly testing achieved seventy six percent sensitivity.
Individual functional assays exhibited exceptional diagnostic specificity ranging from ninety three percent for enzyme assays to ninety nine percent for complex I assembly testing.
Fibroblast testing proved most sensitive for nuclear DNA encoded translation defects cofactor deficiencies and isolated respiratory chain complex impairments while secondary mitochondrial dysfunction remained rare.
Authors concluded that validated skin biopsy functional panels effectively resolve variants of uncertain significance from genome sequencing while sparing patients invasive tissue biopsies.

Summary

This study evaluated the clinical performance and diagnostic utility of comprehensive fibroblast-based functional testing for primary mitochondrial diseases (PMDs). Published in EMBO Molecular Medicine by researchers at Children’s Hospital Colorado and the University of Colorado Anschutz School of Medicine, the investigation addressed the diagnostic limitations of first-line genome sequencing, which yields definitive answers in only 50% to 65% of cases due to variants of uncertain significance. The research sought to systematically evaluate whether skin biopsy-derived fibroblast functional assays could resolve ambiguous genetic findings and replace invasive muscle or liver biopsies across international cohorts.

The clinical validation study analyzed samples from 204 genetically confirmed PMD patients, 51 healthy controls, and 53 patients with non-mitochondrial differential diagnoses across more than 30 medical centers globally. Individual testing modalities exhibited specific diagnostic profiles: respiratory chain enzyme assays demonstrated a sensitivity of 46% and specificity of 93%; blue native polyacrylamide gel electrophoresis (BN-PAGE) showed a sensitivity of 40% and specificity of 98%; and complex I assembly assays achieved a sensitivity of 49% and specificity of 99%. When combined into a comprehensive diagnostic panel, the assays achieved an overall sensitivity of 76%, specificity of 93%, positive predictive value of 96%, and negative predictive value of 67%. Diagnostic sensitivity was highest for isolated respiratory chain deficiencies, nuclear DNA-encoded mitochondrial translation defects, cofactor deficiencies, and mitochondrial aminoacyl-tRNA synthetase disorders.

The authors conclude that comprehensive fibroblast-based functional testing possesses strong clinical utility as a complementary diagnostic tool to genomic sequencing in PMD evaluations. By achieving high specificity and positive predictive value, skin biopsy-derived cell assays effectively resolve uncertain genetic variants while reducing the need for invasive tissue biopsies. These findings establish a validated clinical framework for laboratories to incorporate functional assays into diagnostic algorithms, improving diagnostic yield for patients with suspected inherited metabolic disorders.

Link to the article: https://link.springer.com/article/10.1038/s44321-026-00497-3

References

Van Hove, J. L. K., Friederich, M. W., Van Hove, R. A., Lee, J. C., Knight, K. M., Donovan, T. E., Silveira, L., Ganetzky, R. D., Hirano, M., Abdenur, J., Butler, M. G., Cassiman, D., Cohen, B. H., Elsea, S. H., Enns, G. M., Gahl, W. A., Gavrilova, R., Geddes, G. C., Glamuzina, E. E., … Yang, J. H. (2026). Comprehensive functional testing in fibroblasts has strong utility to diagnose mitochondrial disease. EMBO Molecular Medicine. https://doi.org/10.1038/s44321-026-00497-3