Discussion
The findings in this case report highlight that mT21 is sufficient to induce AD neuropathology and early-onset dementia. Highlights: Trisomy 21 mosaicism (mT21) occurs when three copies of chromosome 21 are present in some but not all somatic cells in an individual. mT21 accounts for ≈ 2% of people diagnosed with Down syndrome (DS). Immunohistochemical identification of amyloid beta, tau, astrocytes, microglia, α-synuclein, and TAR DNA-binding protein 43 show that Alzheimer's disease (AD) pathology in mT21 is similar to full trisomy 21. The findings in this case report highlight that mT21 is sufficient to induce AD neuropathology and early-onset dementia.
Methods
We describe AD neuropathology in mT21 including amyloid beta, phosphorylated tau, astrogliosis, microgliosis, α-synuclein, and TAR DNA-binding protein 43 (TDP-43) in cerebral cortex, hippocampal subregions, and amygdala using immunohistochemistry.
Results
We observed high AD neuropathologic change with a score of A3B3C3. In addition, there was widespread astrogliosis, cerebral amyloid angiopathy, and perivascular space widening throughout the brain. Lewy bodies and neurites were noted in the amygdala only and no TDP-43 was observed.