Neuropsychological functions in variant Alzheimer's disease with spastic paraparesis

[An autopsy case of Alzheimer's disease presenting with corticobasal syndrome]

A right-handed Japanese man developed memory loss at 51 years of age. The right side clumsiness developed from 52 years of age and then progressively worsened. Temporal/parietal lobe atrophy was observed predominantly on the left side upon MR imaging. Subsequently, limb-kinetic apraxia and parkinsonism became apparent predominantly on the right side. These symptoms became aggravated along with dementia, ultimately leading to an apallic state. The patient eventually died at the age of 59 due to aspiration pneumonia. An autopsy was carried out and cerebral atrophy was observed predominantly on the left side. Senile plaques were observed on the entire cerebral cortex at a high frequency, along with many cotton wool plaques. Anti-phosphorylated tau-positive neurofibrillary tangles and several neuropil threads were observed upon immunostaining. The tau-positive structures were also positive for both RD3 and RD4 antibodies. The findings of tauopathy of the glia were poor, and the tau lesion of the brainstem was milder than that of the cerebral cortex. These results suggest the possibility that the corticobasal syndrome clinically developed in some type of Alzheimer's disease and a definite diagnosis was made only by pathological examination.

Cerebellar dysfunction in a family harboring the PSEN1 mutation co-segregating with a cathepsin D variant p.A58V

Presenile dementia may be caused by a variety of different genetic conditions such as familial Alzheimer's disease, prion disease as well as several hereditary metabolic disorders including adult onset neuronal ceroid lipofuscinosis. We report a multigenerational family with autosomal dominant presenile dementia harboring a cerebellar phenotype. Longitudinal clinical work-up in affected family members revealed ataxia accompanied by progressive cognitive decline, rapid loss of global cognition, memory, visuospatial and frontal-executive functions accompanied by progressive motor deterioration and early death. Linkage analysis and exome sequencing identified the p.S170F mutation of Presenilin 1 in all affected individuals, which is known to be associated with very early onset Alzheimer's disease. Additional search for potentially modifying variants revealed in all affected individuals of the third generation a paternally inherited variant p.A58V (rs17571) of Cathepsin D which is considered an independent risk factor for Alzheimer's disease. Involvement of cerebellar and brainstem structures leading to functional decortication in addition to rapid progressive presenile dementia in this PSEN1 family may therefore indicate an epistatic effect of the p.A58V Cathepsin D variant on the deleterious course of this disease.

Variable phenotype of Alzheimer's disease with spastic paraparesis

Pedigrees with familial Alzheimer's disease (AD) show considerable phenotypic variability. Spastic paraparesis (SP), or progressive spasticity of the lower limbs is frequently hereditary and exists either as uncomplicated (paraparesis alone) or complicated (paraparesis and other neurological features) disease subtypes. In some AD families, with presenilin-1 (PSEN1) mutations, affected individuals also have SP. These PSEN1 AD pedigrees frequently have a distinctive and variant neuropathology, namely large, non-cored plaques without neuritic dystrophy called cotton wool plaques (CWP). The PSEN1 AD mutations giving rise to CWP produce unusually high levels of the amyloid beta peptide (Abeta) ending at position 42 or 43, and the main component of CWP is amino-terminally truncated forms of amyloid beta peptide starting after the alternative beta-secretase cleavage site at position 11. This suggests a molecular basis for the formation of CWP and an association with both SP and AD. The SP phenotype in some PSEN1 AD pedigrees also appears to be associated with a delayed onset of dementia compared with affected individuals who present with dementia only, suggesting the existence of a protective factor in some individuals with SP. Variations in neuropathology and neurological symptoms in PSEN1 AD raise the prospect that modifier genes may underlie this phenotypic heterogeneity.

Clinical phenotypic heterogeneity of Alzheimer's disease associated with mutations of the presenilin-1 gene

It is now 10 years since the first report of mutations in the presenilin genes that were deterministic for familial autosomal dominant Alzheimer's disease. The most common of these mutations occurs in the presenilin-1 gene (PSEN1) located on chromosome 14. In the ensuing decade, more than 100 PSEN1 mutations have been described. The emphasis of these reports has largely been on the novelty of the mutations and their potential pathogenic consequences rather than detailed clinical, neuropsychological, neuroimaging and neuropathological accounts of patients with the mutation. This article reviews the clinical phenotypes of reported PSEN1 mutations, emphasizing their heterogeneity, and suggesting that other factors, both genetic and epigenetic,must contribute to disease phenotype.