Skin Biopsy Test Can Diagnose Mitochondrial Disease

Getting a definitive diagnosis for mitochondrial disease has long meant either a lengthy genetic testing journey or an invasive tissue biopsy, and often both without a clear answer. A major international study published in October 2026 changes that picture: functional tests run on skin cells grown from a small biopsy can diagnose mitochondrial disease with 76 percent sensitivity and 93 percent specificity, according to researchers at Children's Colorado and the University of Colorado Anschutz School of Medicine.

Mitochondrial disease describes a group of genetic disorders that cripple the body's ability to produce energy, and it touches roughly one in five thousand people. The conditions are extraordinarily diverse, with variants in more than 360 genes now linked to them, and they can affect nearly any organ system. That heterogeneity has made diagnosis slow and frustrating for families, who often wait years for an answer.

Why genetic testing alone is not enough

Genome sequencing is usually the first step when doctors suspect mitochondrial disease, but it delivers a definitive genetic cause in only about 50 to 65 percent of cases. Many patients get back variants of uncertain significance that geneticists cannot interpret, and roughly a third of patients receive no useful result at all, as reported by MedicalXpress.

Until recently, patients left in that gap were often sent for muscle or liver biopsies so doctors could measure respiratory chain enzyme activity directly in the affected tissue. Those procedures are invasive, sometimes require general anesthesia, and still do not provide a complete picture of mitochondrial function. The new research offers a far gentler route through the same problem.

What a small skin biopsy can reveal

The study evaluated a battery of functional assays on fibroblasts, the cells grown from a small skin biopsy, in more than 200 patients with genetically confirmed mitochondrial disease, alongside 51 healthy controls and 53 patients with other conditions. Samples came from more than 30 medical centers across North America, Europe, Australia and New Zealand, making it one of the largest evaluations of mitochondrial functional testing ever conducted.

The individual assays, which measure respiratory chain enzyme activity, protein assembly and complex structure, were modest on their own. Combined, they reached 76 percent sensitivity, 93 percent specificity, a positive predictive value of 96 percent and a negative predictive value of 67 percent. In plain terms: when the combined testing points toward mitochondrial disease, it is right nearly all of the time.

The testing worked best for isolated respiratory chain deficiencies, defects in mitochondrial protein synthesis and cofactor deficiencies. But the paper is honest about the limits: mitochondrial DNA variants and maintenance disorders remained difficult to detect in skin fibroblasts, meaning the testing complements sequencing rather than replacing it. Functional testing will not end every diagnostic odyssey, but it can confirm suspicious genetic findings and give answers to patients whose sequencing came back empty.

From lab finding to clinical care

This was not a one-center experiment. Nearly all of the functional tests examined in the study are already available through the Mitochondrial Diagnostic Laboratory at Children's Colorado, which the study's authors say is now one of the largest providers of mitochondrial functional testing in North America, accepting samples from medical centers across the United States and Canada. That matters because the distance between a promising research finding and a test a family can actually access is often measured in years; here, it has already been crossed, according to the findings published in EMBO Molecular Medicine.

"For patients and families, reducing the need for invasive procedures is a meaningful advance," said Johan Van Hove, a clinical biochemical genetics specialist at Children's Colorado who led the study with laboratory scientific director Marisa Friederich. The shift from muscle and liver biopsies to a skin biopsy done in a clinic visit could spare children and adults pain, risk and recovery time while giving their doctors the same caliber of functional evidence.

The arc of mitochondrial disease diagnosis now looks like this: decades when muscle and liver biopsies were the standard gave way to the genomics era, which solved half to two thirds of cases. The October 2026 study adds the missing third act, a validated functional layer that can be ordered from a skin sample when genetics falls short. It is the same direction medicine is moving elsewhere, toward less invasive diagnostics: scientists have also shown that a liquid biopsy can detect melanoma's return months before scans. For more on health breakthroughs, see the Health topic page.