Specific amyloid-β42 deposition in the brain of a Gerstmann-Sträussler-Scheinker disease patient with a P105L mutation on the prion protein gene

Although colocalization of amyloid β (Aβ) with prion protein (PrP) in the kuru plaque has previously been observed in the brain of prion diseases patients, the participating Aβ species has not been identified. Here, we present an immunohistochemical assessment of the brain and spinal cord of a 69-year-old Japanese female patient with Gerstmann-Sträussler-Scheinker disease with a P105L mutation on the PRNP gene (GSS-P105L). Immunohistochemical assessment of serial brain sections was performed using anti-PrP and -Aβ antibodies in the hippocampus, frontal and occipital lobes. She died 69 years after a 21-year clinical course. Immunohistochemistorical examination revealed that ~50% of the kuru plaques in the cerebrum were colocalized with Aβ, and Aβ42 was predominantly observed to be colocalized with PrP-plaques. The Aβ deposition patterns were unique, and distinct from diffuse plaques observed in the normal aging brain or Alzheimer’s disease brain. The spinal cord exhibited degeneration in the lateral corticospinal tract, posterior horn, and fasciculus gracilis. We have demonstrated for the first time that Aβ42, rather than Aβ40, is the main Aβ component associated with PrP-plaques, and also the degeneration of the fasciculus gracilis in the spinal cord in GSS-P105L, which could be associated with specific clinical features of GSS-P105L.