Examination of people at risk for the rare familial form of AD may provide clues to how the disease develops in others—years before clinical symptoms appear, according to a recent study. The clues are levels of certain proteins found in plasma and cerebrospinal fluid (CSF), biomarkers that might be used to diagnose AD in its earliest preclinical stage.
The research team, led by scientists at the University of California, Los Angeles, examined blood and CSF samples from 21 adults under age 50, most of whom had no symptoms of AD but were related to people with familial AD, a genetically inherited form of the disease. One of their biomarkers, elevated levels of plasma Aß42 (a type of beta-amyloid protein), also has been found in people with late-onset AD.
The results confirmed and amplified what previous studies have shown: Pre-symptomatic people with the familial-AD mutation had higher levels of plasma Aß42, which declined as the disease progressed, as well as higher plasma Aß42/Aß40 ratios, than those in people without the mutation. People with the mutation had lower CSF Aß42/Aß40 ratios and higher levels of CSF tau and p-tau181 than people who did not carry the mutation. There was no significant difference between the two groups in plasma F2-isoprostane levels.
Ringman, J.M., et al. Biochemical markers in persons with preclinical familial Alzheimer disease. Neurology. 2008 July. 71:85-92.