However, the low abundance of neuronal-derived EVs in circulationand the high levels of soluble L1CAM (sL1CAM) in plasma present challengesfor analysis. Beyond Parkinson'sdisease,L1CAM-expressing neuronal-derived EVs have been implicated in longCOVID, where they contain proteins linked to Alzheimer's disease.Notably, 14 proteins elevated in long COVID were also associated withAD, with six shared proteins (MIF, ENO1, MESD, NUDT5, TNFSF14, andFYB1) specifically linked to cognitive impairment. This evidence concerns the gene L1CAM and early-onset autosomal dominant Alzheimer disease.