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A new case study has opened up a potential new route for researchers to take when examining ways to prevent the most common form of dementia. The case study involved a man who does not produce a protein linked to Alzheimer's disease, known as the apolipoprotein E gene (apoE4). Despite not having the protein, the man does not suffer from cognitive decline or other mental health complications.

Based on previous research, there has been evidence that a mutated apoE can increase one's risk of Alzheimer's disease. Researchers have long questioned whether or not removing the protein completely from the brain could be an effective treatment for Alzheimer's disease. However, up until this case, experts were unsure what would happen if apoE levels fell drastically.

According to the researchers, the 40-year-old man was suffering from several medical problems tied to a rare disorder known as dysbetalipoproteinemia, which hinders the body's ability to process cholesterol and causes xanthomas, which are painful growths that occur when fat accumulate under the skin. He had sought care at the University of California, San Francisco. The researchers discovered that the man had no apoE4 at all but was still "cognitively normal."

"The findings in this patient indicate that completely removing apoE would have no overt ill effects on brain function, and so an Alzheimer's treatment that reduced brain apoE would theoretically have no or little cognitive side effects," Dr. Joachim Herz, a distinguished chair in Alzheimer's disease research at University of Texas Southwestern Medical Center, wrote in an accompanying commentary reported by HealthDay.

Herz added, "The main potential side effect of reducing apoE would be the effect on cholesterol and triglyceride levels. This patient had extremely high levels of both -- something we would have to avoid when treating patients. It would obviously not be beneficial to reduce the risk for Alzheimer's disease if in the process we increase the risk for cardiovascular disease."

The researchers added that the lack of apoE, which can be found in the eye, did not affect the man's vision either. This suggests that removing the gene could be an effective way to prevent the mental illness without hurting other cognitive abilities. However, the researchers cautioned that the man is still relatively young and dementia tends to affect older adults.

The study, "Effects of the Absence of Apolipoprotein E on Lipoproteins, Neurocognitive Function, and Retinal Function," was published in JAMA Neurology.