Which is the pathognomic feature of Alzheimer's disease?
Ans. d. Plaque and tanglesRef: Robbins and Cotran Pathologic Basis of Disease 9th Ed; Page No-1290Alzheimer disease is the most important cause of dementia in elderly.It usually begins after age of 50 years.Most cases are sporadic; only 5-10 of cases are familial.Pneumonia is the most common cause of death.Grossly:Cortical atrophy with narrowed gyri and widened sulci especially in the frontal, temporal, and parietal lobes.Hydrocephalus ex vacuo also occurs due to cortical atrophy.Earliest sites involved are medial temporal lobe structure.Morphologic AbnormalitiesNeurofibrillary tangles (NFT):NFT are bundles of helical filaments in neural cytoplasm.It is hypo phosphorylated tau protein.Especially seen in the cerebral cortex.It is clearly visible by sliver (Bielschowsky) staining.Neuritic (senile) plaques:They are spherical collections of dilated, tortuous, neuritic processes (dystrophic neutrites) within the cerebral cortex, hippocampus, and amygdala.A distinctive peptide structure is present around central amyloid core.Non-specific findings.Increased number of neuritic plaque correlates advanced age and severity of dementia.Granulovacuolar degeneration: is the intraneuronal cytoplasmic granule-containing small and clear vacuoles occurring within the pyramidal cells of the hippocampusAmyloid angiopathy: Almost Invariably accompanies Alzheimer disease. There is vascular p-amyloid deposition.Hirano bodies: Are the intracytoplasmic proximal dendritic eosinophilic inclusions containing actin protein.EtiologyAbnormal amyloid gene expression is the most favored etiologic concept today.Ap40 Aggregates are directly neurotoxic and it will induce synaptic damage of nucleus basalis of mayernet. This will decreases the brain content of the enzyme and its product acetylcholine, especially in the cerebral cortex and hippocampus. Acetylcholine plays a role in learning, and drugs that block its action adversely affect short-term memory.The APP gene located on chromosome 21; it encoded for amyloid precursor protein, a precursor to the Ab peptide. Mutations in the APP gene have been linked to familial Alzheimer disease.Down syndrome patients (trisomy 21) experience early onset Alzheimer disease secondary to gene dosage effect.Other genetic abnormalitiesInheritance of the[?]4 allele of apoprotein E is located in chromosome 19; is associated with greater frequency in patients with Alzheimer disease.Mutations in genes coding for presenilins. Presenilin-1 located in chromosome 14 and presenilin-2 located in chromosome 1 have been associated with many kindreds with familial early onset Alzheimer disease.
Lewy bodies
Pick bodies
Ballooned neurons
Plaque and tangles
Central Nervous System