News Release

CHOP researchers show early developmental delays predict poor long-term outcomes in Leigh syndrome patients

Study makes the case for Leigh syndrome to be considered a potential diagnosis for infants and children with early developmental delays

Peer-Reviewed Publication

Children's Hospital of Philadelphia

Philadelphia, March 1, 2022 – Researchers from the Mitochondrial Medicine Frontier Program at Children’s Hospital of Philadelphia (CHOP) have found that developmental delays associated with Leigh syndrome, the most common pediatric mitochondrial disorder, may occur earlier than previously recognized – even before metabolic stroke and regression – which could provide clinicians with an opportunity for earlier diagnosis and therapeutic interventions. The findings were recently published online by the journal Molecular Genetics and Metabolism.

Leigh syndrome has been characterized by neurodevelopmental regression, when a child loses previously achieved skills and developmental milestones, with metabolic strokes occurring in their deep brain regions typically early in life. Currently, no FDA-approved therapies or cures exist, and developmental delays associated with Leigh syndrome are often the primary symptom studied in clinical trials.

Historically, developmental disabilities were thought to mainly occur after the onset of metabolic stroke and neurologic regression. However, some rare instances have been reported in which primary developmental delays occurring prior to neurologic regression were observed in Leigh syndrome patients. The CHOP researchers decided to examine existing data to see if primary developmental delays were more common than previously believed.

“By looking at the pre-regression history of these patients, we were hoping to see signs that would allow us to diagnose Leigh syndrome at an earlier stage prior to their acute decompensation,” said co-senior author Rebecca Ganetzky, MD, an attending physician, Assistant Professor, and Director of Biochemical Test Development in the Mitochondrial Medicine Frontier Program at CHOP. “Since we found that developmental delays were the presenting symptom for many of these cases, our study demonstrates that mitochondrial energetics impact developmental trajectories prior to their first episode of neurodevelopmental regression.”

Among a cohort of 69 Leigh syndrome patients, 47 had a history of primary developmental delays prior to any regression and 53 had neurodevelopmental regression. The study team identified three distinct phenotypes among these patients: those with primary developmental delays followed by regression (31 patients), primary developmental delays without subsequent regression (16 patients), and regression without primary developmental delays (22 patients). Those with a history of primary developmental delays were more likely to have earlier disease onset and worse long-term educational outcomes.

“This study demonstrates that Leigh syndrome disorders should be considered a diagnostic possibility at the time when a child is recognized to have early developmental delays, even if the child hasn’t yet had a serious regression episode that is often the trigger to begin the diagnostic process,” said study co-author Marni Falk, MD, an attending physician, Professor, Distinguished Chair, and Executive Director of the Mitochondrial Medicine Frontier Program at CHOP. “We hope our findings will lead to prospective natural history studies that examine specific neurodevelopmental outcomes to help us design future clinical trials for therapies to help these patients at as early a stage in their disease course as possible.”

This study was supported by the North American Mitochondrial Disease Consortium (NAMDC) Gateway to Mitochondrial Medicine Grant from the United Mitochondrial Disease Foundation, the CHOP Mitochondrial Medicine Frontier Program, the National Institutes of Health grants K08-DK113250, R35-GM134863, and the Intellectual and Developmental Disabilities Research Center at CHOP/UPENN per NIH/NICHD grants P50 HD105354 and U54-HD086984.

Tinker et al, “Early developmental delay in Leigh Syndrome spectrum disorders is associated with poor clinical prognosis.” Mol Genet Metab. Online February 23, 2022. DOI: 10.1016/j.ymgme.2022.02.006.

About Children’s Hospital of Philadelphia: A non-profit, charitable organization, Children’s Hospital of Philadelphia was founded in 1855 as the nation’s first pediatric hospital. Through its long-standing commitment to providing exceptional patient care, training new generations of pediatric healthcare professionals, and pioneering major research initiatives, the 595-bed hospital has fostered many discoveries that have benefited children worldwide. Its pediatric research program is among the largest in the country. The institution has a well-established history of providing advanced pediatric care close to home through its CHOP Care Network, which includes more than 50 primary care practices, specialty care and surgical centers, urgent care centers, and community hospital alliances throughout Pennsylvania and New Jersey, as well as a new inpatient hospital with a dedicated pediatric emergency department in King of Prussia. In addition, its unique family-centered care and public service programs have brought Children’s Hospital of Philadelphia recognition as a leading advocate for children and adolescents. For more information, visit


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