B2M and primary systemic amyloidosis: Consistent with our models in Alzheimer’s disease participants, B2 M is also directly implicated in pathological amyloid accumulation, including development of systemic amyloidosis,37,38 is a component of the beta-amyloid plaque core, and promotes beta-amyloid aggregation and neurotoxicity in models of Alzheimer’s disease.39 To our knowledge, these are among the first data showing a role for B2 M in FTD suggesting that its neurotoxicity may extend beyond beta-amyloid.