Ballooned neurons expressing alphaB-crystallin as a constant feature of the amygdala in argyrophilic grain disease.

We report the presence of ballooned neurons (BNs) as a constant feature of amygdaloid nuclei in patients with argyrophilic grain disease (AgD). In 10 cases with AgD BNs were randomly dispersed throughout the amygdala and were associated with various numbers of argyrophilic grains (ArGs) and tau immunoreactive non-ballooned neurons. BNs were strongly labelled with antibodies against alphaB-crystallin, phosphorylated tau (AT8, PHF-1) and phosphorylated neurofilament (SMI-31). In contrast AT8-immunoreactive non-ballooned neurons and ArGs remained consistently unstained with the alphaB-crystallin antibody. Our findings suggest that in AgD two different pathological mechanisms may operate in limbic neurons: (1) abnormal phosphorylation of tau protein probably linked to the formation of ArGs without cell ballooning or alphaB-crystallin expression; (2) accumulation of hyperphosphorylated tau protein and alphaB-crystallin expression leading to cell ballooning not related to ArGs formation.