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Updated January 11, 2026 - A years-long investigation into a suspected neurological syndrome in New Brunswick has concluded that the condition does not exist, leaving hundreds of patients grappling with misdiagnoses and unresolved health struggles.
The emergence of a medical mystery
In early 2019, health officials in New Brunswick detected two cases of Creutzfeldt-Jakob Disease (CJD), a rare and fatal brain disorder. While the cases did not spread, neurologist Alier Marrero reported observing similar symptoms in over 20 patients, including young individuals with rapidly progressing dementia. By 2024, the number of suspected cases had grown to 500, prompting a federal investigation.
Patients exhibited a wide range of symptoms: dementia, weight loss, muscle spasms, hallucinations, and even Capgras Delusion-a condition where individuals believe loved ones have been replaced by impostors. Some lost the ability to speak or write, while others experienced extreme sensory distortions, such as perceiving cold water as scalding hot.
A cluster without a cause
Initial suspicions centered on environmental toxins, including glyphosate, a herbicide widely used in New Brunswick's forestry industry. Marrero reported elevated levels of glyphosate and heavy metals in many patients, though he did not disclose exact figures. Despite extensive testing, no definitive cause was identified.
A 2021 federal-provincial collaboration, backed by $5 million in funding from the Canadian Institutes of Health Research (CIHR), was abruptly halted when New Brunswick withdrew from the partnership. Provincial officials cited concerns over Marrero's methods and the informal nature of the investigation.
The collapse of the mystery disease theory
In May 2025, a study published in the Journal of the American Medical Association (JAMA) delivered a decisive verdict: the New Brunswick cluster was not a new disease but a series of misdiagnoses. Researchers, including neuropathologist Gerard Jansen, found that all 25 patients examined-both living and deceased-had known conditions such as Alzheimer's, Lewy body dementia, or functional neurological disorder (FND).
"The probability of there being no new disease is close to 100%. The real cause was serial misdiagnosis."
Dr. Anthony Lang, lead researcher
Jansen, who had previously raised concerns about the cluster, stated that the patients' symptoms aligned with established neurological and psychiatric disorders. The study concluded that the misdiagnosis was exacerbated by media sensationalism, institutional distrust, and the influence of patient advocacy groups.
Patients divided over the findings
Many patients, fiercely loyal to Marrero, rejected the study's conclusions. Some, like Jillian Lucas, believe they were exposed to an environmental toxin and accuse the government of a cover-up. Lucas, whose symptoms worsened under Marrero's care, has since pursued medical assistance in dying (MAID), a legal option in Canada even without a terminal diagnosis.
Others, however, accepted alternative diagnoses. Sandi Partridge was initially diagnosed with the mystery illness but later learned she had FND, a condition where psychological distress manifests as physical symptoms. After intensive therapy, she reported significant improvement.
A neurologist's unwavering conviction
Despite the mounting evidence against the existence of the syndrome, Marrero remains convinced of its reality. He continues to see new patients, arguing that the scientific community has abandoned them. "I keep going because I know," he told the BBC. "I have met with some of the best scientists in the country."
Critics, however, argue that Marrero's persistence has harmed patients. Dr. Anthony Lang, who diagnosed Gabrielle Cormier-one of the youngest patients-with FND, stated that the misdiagnosis led to unnecessary treatments, including powerful immunosuppressants that caused severe side effects.
The human cost of misdiagnosis
For patients like Lucas, the lack of a clear diagnosis has been devastating. Confined to her home, she describes her life as "very limited," with little hope for recovery. Meanwhile, patient advocates, such as Kat Lanteigne of Bloodwatch, continue to pressure the government for answers, alleging a conspiracy to suppress the truth.
A forthcoming provincial report may provide clarity, particularly regarding claims of elevated glyphosate and heavy metal exposure. Until then, the debate over New Brunswick's mystery disease remains unresolved, leaving patients and families in limbo.
