DIFFERENTIAL SUSCEPTIBILITY TO NEUROFIBRILLARY PATHOLOGY AMONG PATIENTS WITH DOWN-SYNDROME

Individual differences in the development of neurofibrillary changes w ere examined in eight cortical regions in the brains of 43 subjects wi th Down syndrome (DS; age range, 15-69 years) using sections stained w ith monoclonal antibodies (mAb) tau-1 and 3-39, Neurofibrillary pathol ogy was found in 4 cases below 36 years of age and in all 20 cases abo ve that age. In the 24 positive cases, numerical density of pretangles stained with tau-1 and 3-39, respectively, was 6.1/mm(2) and 0/mm(2); early tangles, 5.0/mm(2) and 5.3/mm(2); mature tangles, 4.0/mm(2) and 5.0/mm(2) (p < 0.01); and end-stage tangles, 0.04/mm(2) and 2.5/mm(2) (p < 0.001). Numerical density of pretangles stained with mAb tau-l a nd tangles and plaques stained with mAb 3-39 correlates weakly with ag e (r = 0.43; p < 0.02), and together with the wide range of numerical densities suggested heterogeneity of the population examined. Cluster analysis based on two variables - i.e., numerical density of pretangle s stained with mAb tau-l and neurofibrillary tangles (NFTs) and plaque s stained with mAb 3-39, distinguished three groups of subjects with s evere, moderate and weak changes. The severely affected group of 5 sub jects (21%) had an average 54.6/mm(2) of neurons and 13.9/mm(2) plaque s with neurofibrillary changes, whereas the moderately affected group (6 subjects; 25%) showed a significantly lower numerical density of ne urons and plaques with neurofibrillary changes (25.7/mm(2) and 8.1/mm( 2), respectively) as compared with the most affected group. Most of th e subjects (13; 54%) belong to the third group with only 2.2/mm(2) of neurons and 1.4/mm(2) plaques with neurofibrillary pathology. Comparis on of these three groups of Down syndrome subjects representing high, moderate, and low susceptibility to neurofibrillary changes with the g eneral population suggests that the risk of Alzheimer disease is simil ar but the onset of pathological changes is earlier in DS.