PDCD6IP and early-onset autosomal dominant Alzheimer disease: In Alzheimer's disease, some types of exosomes appear to promote disease progression while others appear to prevent the progression.[71] Exosomes are enriched in Alzheimer's disease plaques—aggregates of β‐amyloid protein in the brain which cause synaptic signal blocking—as evidenced by high concentrations of the exosomal protein marker ALIX in these plaques.