Usually in people with Alzheimer’s, beta-amyloid (a protein) is found in large quantities outside of neurons and tau “tangles” are found inside axons – the long projection of neurons. However, in this case, scans failed to show any such features in the boy’s brain.

The researchers found abnormally high levels of a protein called p-tau181 in the patient’s cerebrospinal fluid. This is usually seen before the formation of tau “tangles” in the brain. The brain scans also revealed that the boy’s hippocampus – a part of the brain involved in memory – had shrunk. This is a common early sign of dementia.