Abstract
A rare adult autopsy case of Down syndrome was reported. The patient was a 36-year-old male, whose chromosome analysis revealed 47, XY, +21. He showed typical systemic AA-amyloidosis and numerous senile plaques in the brain. Senile plaques were diffuse or primitive. They were composed of β-protein, but negative for Congo-red stain. There were few neurofibrillary changes in the para hippocampal gyri. Nucleus basalis Meynert showed no significant lesion. The distribution of these plaques had some characteristics different from that for Alzheimer's disease. In the brain involvement of systemic AA-amyloidosis was restricted to the regions devoid of blood-brain-barrier, such as choroid plexus and pituitary gland. Cerebral β-amyloid and systemic amyloid A protein were segregated on each side of the blood-brain-barrier. Therefore, we suggested that each amyloid might be synthesized and deposited by its own mechanism. Electronmicroscopically Hirano's body was identified in the hippocampal gyri.
