Pick body disease and Pick syndrome.

Diagnostic criteria for Pick's disease have been criticized from many different viewpoints. This confusion is mainly derived from the ambiguity of this term 'Pick's disease' (PD), which may imply either purely histological findings, such as Pick body (PB), or a characteristic clinical syndrome that could occur even in the absence of PB. This taxonomic confusion will be circumvented by introducing the diagnostic term 'Pick body disease' to designate patients with the characteristic argyrophilic inclusions purely on histological grounds. In parallel, employment of 'Pick syndrome' to describe the time-honored clinical features may be more convenient and less confusing than PD because PD implies either the presence of PB or the clinical features, two aspects not necessarily linked to each other. Three-dimensional reconstruction of PB confirmed that tau-like immunoreactivity was accentuated at their periphery, as was recognized with the Bodian method. Preferential affinity of three-repeat tau pathology, as seen in Pick body disease, to the Bodian over the Gallyas method is distinct from the reversed affinity (the Gallyas over the Bodian method) of four-repeat tau pathology, as seen in corticobasal degeneration and in argyrophilic grains. This preference of silver staining is compatible with the mixed three- and four-repeat tau pathology, as seen in NFT of the Alzheimer's type, which are stained with both the Bodian and Gallyas staining. This will provide a practical basis on which to differentiate these disorders based on their distinctive tau species and possible relation of tau species to staining profile on these silver methods.