According to a recent case study published in the Journal of Alzheimer’s Disease, a 19-year-old man from China who has been experiencing memory problems since the age of 17 has been diagnosed with dementia.
After conducting various tests, researchers at the Capital Medical University in Beijing diagnosed the teenager with “probable” Alzheimer’s disease. If confirmed, he would be the youngest person ever recorded with the disease, as the primary risk factor for Alzheimer’s is age.
While the exact causes of Alzheimer’s are still largely unknown, a key characteristic of the disease is the buildup of two proteins in the brain, beta-amyloid, and tau. In individuals with Alzheimer’s, beta-amyloid is commonly found in large quantities outside of brain cells, while tau “tangles” are located within axons, which are the long and slender projections of neurons.
Although scans did not reveal any signs of beta-amyloid or tau tangles in the 19-year-old’s brain, researchers found elevated levels of a protein called p-tau181 in his cerebrospinal fluid. This is a precursor to the formation of tau tangles in the brain.
In people under the age of 30, nearly all cases of Alzheimer’s disease are caused by inherited faulty genes. The previous youngest case, a 21-year-old, had a genetic cause.
Three genes – amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) – have been linked to Alzheimer’s disease in young people. These genes produce a protein fragment known as a beta-amyloid peptide, which is a precursor to beta-amyloid. If the gene is faulty, it can result in an abnormal buildup of beta-amyloid in the brain, which is a hallmark of Alzheimer’s disease and a target for treatments like the recently approved drug lecanemab.
To develop Alzheimer’s disease, a person only needs to have one of the APP, PSEN1, or PSEN2 genes to be faulty. Their offspring also have a 50:50 chance of inheriting the gene and developing the disease.
However, a genetic cause was ruled out in the case of the 19-year-old Chinese man with dementia. Researchers conducted a whole-genome sequence on the patient but failed to find any known genetic mutations. Additionally, no one in his family had a history of Alzheimer’s disease or dementia. The patient did not have any other diseases, infections, or head trauma that could explain his condition. It appears that his form of Alzheimer’s is extremely rare.
The patient began experiencing problems concentrating on his studies at age 17, followed by a loss of short-term memory at age 18. He couldn’t remember if he had eaten or completed his homework. His memory loss became so severe that he had to drop out of high school during his final year. Standard cognitive tests confirmed a probable diagnosis of Alzheimer’s disease and showed severe impairment of his memory. Brain scans also revealed that his hippocampus, a region of the brain involved in memory, had shrunk, which is a typical early sign of dementia.