Familial Early-Onset Alzheimer's Caused by Novel Genetic Variant and APP Duplication: A Cross-Sectional Study

BACKGROUND

The clinical characteristics of symptomatic and asymptomatic carriers of early- onset autosomal dominant Alzheimer's (EOADAD) due to a yet-undescribed chromosomal rearrangement may add to the available body of knowledge about Alzheimer's disease and may enlighten novel and modifier genes. We report the clinical and genetic characteristics of asymptomatic and symptomatic individuals carrying a novel APP duplication rearrangement.

METHODS

Individuals belonging to a seven-generation pedigree with familial cognitive decline or intracerebral hemorrhages were recruited. Participants underwent medical, neurological, and neuropsychological evaluations. The genetic analysis included chromosomal microarray, Karyotype, fluorescence in situ hybridization, and whole genome sequencing.

RESULTS

Of 68 individuals, six females presented with dementia, and four males presented with intracerebral hemorrhage. Of these, nine were found to carry Chromosome 21 copy number gain (chr21:27,224,097-27,871,284, GRCh37/hg19) including the APP locus (APP-dup). In seven, Chromosome 5 copy number gain (Chr5: 24,786,234-29,446,070, GRCh37/hg19) (Chr5-CNG) cosegregated with the APP-dup. Both duplications co-localized to chromosome 18q21.1 and segregated in 25 pre-symptomatic carriers. Compared to non-carriers, asymptomatic carriers manifested cognitive decline in their mid-thirties. A third of the affected individuals carried a diagnosis of a dis-immune condition.

CONCLUSION

APP extra dosage, even in isolation and when located outside chromosome 21, is pathogenic. The clinical presentation of APP duplication varies and may be gender specific, i.e., ICH in males and cognitive-behavioral deterioration in females. The association with immune disorders is presently unclear but may prove relevant. The implication of Chr5-CNG co-segregation and the surrounding chromosome 18 genetic sequence needs further clarification.

Determinants of Caregiver Burden in Early-Onset Dementia

Introduction

Caregivers of patients with early-onset dementia (EOD) experience high levels of burden, which is known to be affected by caregivers' psychological features as well as by patients' and caregivers' demographical and social variables. Although potential clinical, demographical, and social determinants have been separately examined, it is not known how they reciprocally interact.

Methods

Ninety-two consecutive patient-caregiver dyads were recruited from the Cognitive Neurology Clinics of Modena, Northern Italy. Caregivers were asked to fill in questionnaires regarding their burden, psychological distress, and family economic status. Data were analyzed with multivariable regression models and then entered in a mediation model.

Results

Caregiver burden was positively related to female caregiver sex, spousal relationship to the patient, severity of patient's behavioral symptoms, diagnostic delay, and financial distress of the family. It was negatively related to disease duration, patient's education, region of birth, caregiver age, number of caregiver's days off work, number of offspring, and caregiver perception of patient's quality of life. While the effect of caregiver age, diagnostic delay, and of proxies of family or social network directly impacted on caregiver's burden, the effect of patient's disease duration, being a wife caregiver, financial distress, and number of caregiver's days off work was entirely mediated by the level of caregiver psychological distress.

Conclusions

Both direct actions (such as increasing social networks and shortening diagnostic delay) and indirect actions aimed at reducing psychological distress (such as increasing the number of caregiver's days off work and financial support) should be planned to reduce caregiver's burden.

Longitudinal brain atrophy and CSF biomarkers in early-onset Alzheimer's disease

There is evidence of longitudinal atrophy in posterior brain areas in early-onset Alzheimer's disease (EOAD; aged < 65 years), but no studies have been conducted in an EOAD cohort with fluid biomarkers characterization. We used 3T-MRI and Freesurfer 6.0 to investigate cortical and subcortical gray matter loss at two years in 12 EOAD patients (A + T + N + ) compared to 19 controls (A-T-N-) from the Hospital Clínic Barcelona cohort. We explored group differences in atrophy patterns and we correlated atrophy and baseline CSF-biomarkers levels in EOAD. We replicated the correlation analyses in 14 EOAD (A + T + N + ) and 55 late-onset AD (LOAD; aged ≥ 75 years; A + T + N + ) participants from the Alzheimer's disease Neuroimaging Initiative. We found that EOAD longitudinal atrophy spread with a posterior-to-anterior gradient and beyond hippocampus/amygdala. In EOAD, higher initial CSF NfL levels correlated with higher ventricular volumes at baseline. On the other hand, higher initial CSF Aβ42 levels (within pathological range) predicted higher rates of cortical loss in EOAD. In EOAD and LOAD subjects, higher CSF t-tau values at baseline predicted higher rates of subcortical atrophy. CSF p-tau did not show any significant correlation. In conclusion, posterior cortices, hippocampus and amygdala capture EOAD atrophy from early stages. CSF Aβ42 might predict cortical thinning and t-tau/NfL subcortical atrophy.

A novel presenilin 1 duplication mutation (Ile168dup) causing Alzheimer's disease associated with myoclonus, seizures and pyramidal features

Mutations in the Presenilin 1 (PSEN1) gene are the most common cause of autosomal dominant familial Alzheimer's disease. We report the clinical, imaging and postmortem findings of kindred carrying a novel duplication mutation (Ile168dup) in the PSEN1 gene. We interpret the pathogenicity of this novel variant and discuss the additional neurological features (pyramidal dysfunction, myoclonus and seizures) that accompanied cognitive decline. This report broadens the clinical phenotype of PSEN1 insertion mutations while also highlighting the importance of considering duplication, insertion and deletion mutations in cases of young onset dementia.

Early-onset Alzheimer's disease may be associated with sortilin-related receptor 1 gene mutation: A family report and review

Background: Early-onset Alzheimer's disease is a rare condition that differs from the usual memory-disordered presentation of typical Alzheimer's disease. Early-onset Alzheimer's disease is believed to have a genetic basis, and sporadic Alzheimer's disease has been associated with sortilin-related receptor 1 polymorphism.

Case presentation: This report describes and discusses the family report of a 59-year-old patient with early-onset Alzheimer's disease that may have been associated with a sortilin-related receptor 1 gene mutation. The patient was hospitalized in August 2008 for gradually progressive amnesia. Brain magnetic resonance imaging showed that the patient presented with whole-brain atrophy (especially in the bilateral medial temporal lobe and hippocampus). He had an initial Mini-Mental State Examination score of 15 (time orientation: 4/5; place orientation: 4/5; language immediate memory: 2/3; attention and calculation: 1/5; delayed memory: 0/3; naming: 1/2; language retelling, understanding, and expression: 3/6; visuospatial ability: 0/1). Whole-exome sequencing showed a sortilin-related receptor 1 gene mutation, c.3575G>A (chr11:121448104), which was detected in the patient and his children.

Discussion: Patients with early-onset Alzheimer's disease present with obvious deficits in language, visuospatial abilities, praxis, or other nonmemory cognitive functions. In this case, the speech, memory, and visuospatial impairment of the patient may be associated with the sortilin-related receptor 1 gene mutation. Atrophy of the bilateral medial temporal lobe/hippocampus on magnetic resonance imaging may be an important marker of early-onset Alzheimer's disease. A sortilin-related receptor 1 gene mutation, c.3575G>A (chr11:121448104), may increase the risk of Alzheimer's disease.

Probable Novel PSEN1 Gln222Leu Mutation in a Chinese Family with Early-Onset Alzheimer's Disease

BACKGROUND

The rate of occurrence of Alzheimer's disease is increasing around the world. However, there is still no significant breakthrough in the study of its etiology and pathogenesis.

OBJECTIVE

To screen Alzheimer's disease pathogenic genes, which may be conducive to the elucidation of the pathogenic mechanisms of Alzheimer's disease And predict the pathogenicity by various computer software.

METHODS

Clinical and neuroimaging examination, Whole Exome Sequencing, and Sanger sequencing were performed in the proband. Mutation sites were verified in 158 subjects.

RESULTS

We reported a proband carrying a probably novel pathogenic mutation, which clinically manifests as progressive memory loss, visual-spatial disorders, apraxia, psychobehavioral disorders, and temperamental and personality changes. Whole Exome Sequencing detected a novel missense mutation at codon 222 (Q222L), which is a heterozygous A to T point mutation at position 665 (c.665A>T) in exon 5 of the presenilin 1 leading to a glutamine-to-leucine substitution. The mutation was also identified by Sanger sequencing in one family member; nevertheless, it was not detected in the other 7 unaffected family members, 50 sporadic Alzheimer's disease patients and 100 control subjects.

CONCLUSION

A novel mutation in exon 5 of the presenilin 1 gene (Gln222Leu) in a Chinese family with early-onset Alzheimer's disease has been reported, besides， it was predicted that the missense mutation was probably a novel pathogenic mutation that was reported for the first time in a Chinese family with early-onset Alzheimer's disease.

Hemorrhagic stroke and COVID-19 infection: Coincidence or causality?

Amyloid Protein Precursor gene duplication is a rare cause of early-onset Alzheimer's disease that can be associated with Cerebral Amyloid Angiopathy. This condition predisposes cerebrovascular events, specifically, intracerebral hemorrhagic stroke. This report describes a case of first-time intracerebral hemorrhage in a patient with APP gene duplication during SARS-CoV-2 infection, a typically pro-thrombotic and pro-inflammatory condition, as a possible trigger for this condition.

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Stroke could be triggered by COVID-19 infection in high-risk patients.

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Altered level of consciousness could be the first manifestation of COVID-19.

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CT thorax scan must be considered during neuroimaging studies in stroke patients.

Plasma biomarkers of astrocytic and neuronal dysfunction in early- and late-onset Alzheimer's disease

INTRODUCTION

We investigated plasma proteomic markers of astrocytopathy, brain degeneration, plasticity, and inflammation in sporadic early-onset versus late-onset Alzheimer's disease (EOAD and LOAD).

METHODS

Plasma was analyzed using ultra-sensitive immuno-based assays from 33 EOAD, 30 LOAD, and 36 functionally normal older adults.

RESULTS

Principle component analyses identified 3 factors: trophic (BDNF, VEGF, TGFβ), degenerative (GFAP, NfL), and inflammatory (TNFα, IL-6, IP-10, IL-10). Trophic factor was elevated in both AD groups and associated with cognition and gray matter volumes. Degenerative factor was elevated in EOAD, with higher levels associated with worse functioning in this group. Biomarkers of inflammation were not significantly different between groups and were only associated with age.

DISUCSSION

Plasma proteomic biomarkers provide novel means of investigating molecular processes in vivo and their contributions to clinical outcomes. We present initial investigations of several of these fluid biomarkers, capturing aspects of astrocytopathy, neuronal injury, cellular plasticity, and inflammation in EOAD versus LOAD.

A novel V272D presenilin mutation associated with logopenia, disorientation, and apraxia in an autosomal-dominant Alzheimer's disease family

In the present study, a novel mutation in the presenilin 1 gene was discovered in an Iraq-native patient with early-onset Alzheimer's disease, who presented with speech impairment and memory decline at age 46 years. Magnetic resonance imaging showed a frontotemporal atrophy. Sanger sequencing identified a heterozygous T to A transversion at position 815 (c.815T>A) in the presenilin 1 gene (PSEN1), resulting in a novel missense mutation at codon 272 from valine to aspartate (V272D). We tested this PSEN1 mutation in vitro and found V272D resulted in an altered Aβ42/40 ratio.

A patient with early-onset Alzheimer's disease with a novel PSEN1 p.Leu424Pro mutation

"Presenilin 1" (PSEN1) gene mutations are the major known genetic cause of early-onset Alzheimer's disease. Herein, we report a novel heterozygous PSEN1 mutation (p.Leu424Pro) in a Turkish patient presenting with deterioration of short-term memory and visuospatial skills starting at the age of 47 years. This novel mutation is located in the conserved residue of transmembrane domain 8 coded by exon 12. At the protein level, this mutation caused a disruption in the alpha helix structure of PSEN1. The structural and possible functional consequences of the mutation suggest that it has probably a pathogenic effect, which in turns had a potential role in the development of Alzheimer's disease in our patient.

Analysis of dementia-related gene variants in APOE ε4 noncarrying Korean patients with early-onset Alzheimer's disease

There is a genetic overlap among various neurodegenerative diseases that cause dementia. We analyzed dementia-related gene variants in 60 apolipoprotein E ε4 non-carrying Korean patients with early-onset Alzheimer's disease. Thirty-one dementia-related genes were screened by exome sequencing. Among the 60 patients, three likely pathogenic variants (LPVs) and 1 variant of uncertain significance (VUS) were identified in PSEN1. In addition, two LPVs in TYROBP (c.141del) and PINK1 (c.1220G>A) and 17 VUS were found in other dementia-causing genes. Two variants in SORL1 and TREM2 were identified that were associated with Alzheimer's disease. In this study, we identified 5 (8.3%) LPVs and 18 (30%) VUSs in known dementia-related genes in apolipoprotein E ε4 noncarrying Korean patients with early-onset Alzheimer's disease.

Genetic screening in early-onset Alzheimer's disease identified three novel presenilin mutations

Mutations in presenilin 1 (PSEN1), presenilin 2 (PSEN2), and amyloid precursor protein (APP) are major genetic causes of early-onset Alzheimer's disease (EOAD). Clinical heterogeneity is frequently observed in patients with PSEN1 and PSEN2 mutations. Using whole exome sequencing, we screened a Dutch cohort of 68 patients with EOAD for rare variants in Mendelian Alzheimer's disease, frontotemporal dementia, and prion disease genes. We identified 3 PSEN1 and 2 PSEN2 variants. Three variants, 1 in PSEN1 (p.H21Profs*2) and both PSEN2 (p.A415S and p.M174I), were novel and absent in control exomes. These novel variants can be classified as probable pathogenic, except for PSEN1 (p.H21Profs*2) in which the pathogenicity is uncertain. The initial clinical symptoms between mutation carriers varied from behavioral problems to memory impairment. Our findings extend the mutation spectrum of EOAD and underline the clinical heterogeneity among PSEN1 and PSEN2 mutation carriers. Screening for Alzheimer's disease-causing genes is indicated in presenile dementia with an overlapping clinical diagnosis.

Differences in hippocampal subfield volume are seen in phenotypic variants of early onset Alzheimer's disease

The most common presentation of early onset Alzheimer's disease (EOAD - defined as symptom onset <65 years) is with progressive episodic memory impairment - amnestic or typical Alzheimer's disease (tAD). However, EOAD is notable for its phenotypic heterogeneity, with posterior cortical atrophy (PCA) - characterised by prominent higher-order visual processing deficits and relative sparing of episodic memory - the second most common canonical phenotype. The hippocampus, which comprises a number of interconnected anatomically and functionally distinct subfields, is centrally involved in Alzheimer's disease and is a crucial mediator of episodic memory. The extent to which volumes of individual hippocampal subfields differ between different phenotypes in EOAD is unclear. The aim of this analysis was to investigate the hypothesis that patients with a PCA phenotype will exhibit differences in specific hippocampal subfield volumes compared to tAD. We studied 63 participants with volumetric T1-weighted MRI performed on the same 3T scanner: 39 EOAD patients [27 with tAD and 12 with PCA] and 24 age-matched controls. Volumetric estimates of the following hippocampal subfields for each participant were obtained using Freesurfer version 6.0: CA1, CA2/3, CA4, presubiculum, subiculum, hippocampal tail, parasubiculum, the molecular and granule cell layers of the dentate gryus (GCMLDG), the molecular layer, and the hippocampal amygdala transition area (HATA). Linear regression analyses comparing mean hippocampal subfield volumes between groups, adjusting for age, sex and head size, were performed. Using a Bonferonni-corrected p-value of p < 0.0025, compared to controls, tAD was associated with atrophy in all hippocampal regions, except the parasubiculum. In PCA patients compared to controls, the strongest evidence for volume loss was in the left presubiclum, right subiculum, right GCMLDG, right molecular layer and the right HATA. Compared to PCA, patients with tAD had strong evidence for smaller volumes in left CA1 and left hippocampal tail. In conclusion, these data provide evidence that hippocampal subfield volumes differ in different phenotypes of EOAD.

Linkage analysis of multiplex Caribbean Hispanic families loaded for unexplained early-onset cases identifies novel Alzheimer's disease loci

Introduction

Less than 10% of early-onset Alzheimer's disease (EOAD) is explained by known mutations.

Methods

We conducted genetic linkage analysis of 68 well-phenotyped Caribbean Hispanic families without clear inheritance patterns or mutations in APP, PSEN1, and PSEN2 and with two or more individuals with EOAD.

Results

We identified 16 (logarithm of odds > 3.6) linked regions, including eight novel loci for EOAD (2p15, 5q14.1, 11p15.1, 13q21.22, 13q33.1, 16p12.1, 20p12.1, and 20q11.21) and eight regions previously associated with late-onset Alzheimer's disease. The strongest signal was observed at 16p12.1 (25 cM, 33 Mb; heterogeneity logarithm of odds = 5.3), ∼3 Mb upstream of the ceroid lipofuscinosis 3 (CLN3) gene associated with juvenile neuronal ceroid lipofuscinosis (JNCL), which functions in retromer trafficking and has been reported to alter intracellular processing of the amyloid precursor protein.

Discussion

This study supports the notion that the genetic architectures of unexplained EOAD and late-onset AD overlap partially, but not fully.

Patterns of progressive atrophy vary with age in Alzheimer's disease patients

Age is not only the greatest risk factor for Alzheimer's disease (AD) but also a key modifier of disease presentation and progression. Here, we investigate how longitudinal atrophy patterns vary with age in mild cognitive impairment (MCI) and AD. Data comprised serial longitudinal 1.5-T magnetic resonance imaging scans from 153 AD, 339 MCI, and 191 control subjects. Voxel-wise maps of longitudinal volume change were obtained and aligned across subjects. Local volume change was then modeled in terms of diagnostic group and an interaction between group and age, adjusted for total intracranial volume, white-matter hyperintensity volume, and apolipoprotein E genotype. Results were significant at p < 0.05 with family-wise error correction for multiple comparisons. An age-by-group interaction revealed that younger AD patients had significantly faster atrophy rates in the bilateral precuneus, parietal, and superior temporal lobes. These results suggest younger AD patients have predominantly posterior progressive atrophy, unexplained by white-matter hyperintensity, apolipoprotein E, or total intracranial volume. Clinical trials may benefit from adapting outcome measures for patient groups with lower average ages, to capture progressive atrophy in posterior cortices.

Polygenic risk score of sporadic late-onset Alzheimer's disease reveals a shared architecture with the familial and early-onset forms

OBJECTIVE

To determine whether the extent of overlap of the genetic architecture among the sporadic late-onset Alzheimer's Disease (sLOAD), familial late-onset AD (fLOAD), sporadic early-onset AD (sEOAD), and autosomal dominant early-onset AD (eADAD).

METHODS

Polygenic risk scores (PRSs) were constructed using previously identified 21 genome-wide significant loci for LOAD risk.

RESULTS

We found that there is an overlap in the genetic architecture among sEOAD, fLOAD, and sLOAD. The highest association of the PRS and risk (odds ratio [OR] = 2.27; P = 1.29 × 10-7) was observed in sEOAD, followed by fLOAD (OR = 1.75; P = 1.12 × 10-7) and sLOAD (OR = 1.40; P = 1.21 × 10-3). The PRS was associated with cerebrospinal fluid ptau181-Aβ42 on eADAD (P = 4.36 × 10-2).

CONCLUSION

Our analysis confirms that the genetic factors identified for LOAD modulate risk in sLOAD and fLOAD and also sEOAD cohorts. Specifically, our results suggest that the burden of these risk variants is associated with familial clustering and earlier onset of AD. Although these variants are not associated with risk in the eADAD, they may be modulating age at onset.

Genetic screening in two Iranian families with early-onset Alzheimer's disease identified a novel PSEN1 mutation

A subset of early-onset Alzheimer's disease is inherited as an autosomal-dominant trait and is associated with mutations in the genes encoding β-amyloid precursor protein, presenilin 1, or presenilin 2. In this study, we identified 2 PSEN1 mutations (1 novel and 1 known) in 2 unrelated Iranian families with autosomal-dominant Alzheimer's disease. The disease progressed rapidly with a mean age at onset of 33 and 42 years and an age at death ranging from 43 to 48 years.

Immune hyperreactivity of Aβ plaque-associated microglia in Alzheimer's disease

Alzheimer's disease (AD) is strongly associated with microglia-induced neuroinflammation. Particularly, Aβ plaque-associated microglia take on an "activated" morphology. However, the function and phenotype of these Aβ plaque-associated microglia are not well understood. We show hyperreactivity of Aβ plaque-associated microglia upon systemic inflammation in transgenic AD mouse models (i.e., 5XFAD and APP23). Gene expression profiling of Aβ plaque-associated microglia (major histocompatibility complex II⁺ microglia) isolated from 5XFAD mice revealed a proinflammatory phenotype. The upregulated genes involved in the biological processes (gene ontology terms) included: "immune response to external stimulus" such as Axl, Cd63, Egr2, and Lgals3, "cell motility", such as Ccl3, Ccl4, Cxcr4, and Sdc3, "cell differentiation", and "system development", such as St14, Trpm1, and Spp1. In human AD tissue with similar Braak stages, expression of phagocytic markers and AD-associated genes, including HLA-DRA, APOE, AXL, TREM2, and TYROBP, was higher in laser-captured early-onset AD (EOAD) plaques than in late-onset AD plaques. Interestingly, the nonplaque parenchyma of both EOAD and late-onset AD brains, the expression of above-mentioned markers were similarly low. Here, we provide evidence that Aβ plaque-associated microglia are hyperreactive in their immune response and phagocytosis in the transgenic AD mice as well as in EOAD brain tissue. We suggest that Aβ plaque-associated microglia are the primary source of neuroinflammation related to AD pathology.

A novel presenilin 1 mutation (F388L) identified in a Chinese family with early-onset Alzheimer's disease. Neurobiol Aging. 2017;50:168.e1-168.e4. [PMID: 27836335 DOI: 10.1016/j.neurobiolaging.2016.10.010]

A subset of Alzheimer's disease (AD) occurrence shows autosomal dominant, familial inheritance patterns. Such familial AD (FAD) are caused by mutations in APP, PSEN1, and PSEN2 genes, which encode amyloid-β (Aβ) precursor protein, presenilin 1 (PS1), and presenilin 2 (PS2), respectively. Here, we report a novel PSEN1 mutation (c.1164C > G, p.F388L, mutation nomenclature according to National Center for Biotechnology Information Reference Sequence: NM_000021.3) occurring in a Chinese family with early-onset AD and cosegregating with affected family members. The average age at onset of this family was 43 years. The F388L mutation locates adjacent to the critical catalytic aspartate site (D385) of PS1. Overexpression of the F388L mutant significantly increased Aβ42 secretion and the ratio of Aβ42/Aβ40 when compared with wild type PS1, consisting with the notion that FAD-associated PS1 mutations induce disease pathogenesis by increasing Aβ42/Aβ40 ratio. Our results identify a novel pathogenic PS1 F388L mutation in a Chinese FAD family.

Early-onset and late-onset Alzheimer's disease are associated with distinct patterns of memory impairment

The goal of this study was to investigate the specific patterns of memory breakdown in patients suffering from early-onset Alzheimer's disease (EOAD) and late-onset Alzheimer's disease (LOAD). Twenty EOAD patients, twenty LOAD patients, twenty matched younger controls, and twenty matched older controls participated in this study. All participants underwent a detailed neuropsychological assessment, an MRI scan, an FDG-PET scan, and AD patients had biomarkers as supporting evidence of both amyloïdopathy and neuronal injury. Results of the neuropsychological assessment showed that both EOAD and LOAD groups were impaired in the domains of memory, executive functions, language, praxis, and visuoconstructional abilities, when compared to their respective control groups. EOAD and LOAD groups, however, showed distinct patterns of memory impairment. Even though both groups were similarly affected on measures of episodic, short term and working memory, in contrast semantic memory was significantly more impaired in LOAD than in EOAD patients. The EOAD group was not more affected than the LOAD group in any memory domain. EOAD patients, however, showed significantly poorer performance in other cognitive domains including executive functions and visuoconstructional abilities. A more detailed analysis of the pattern of semantic memory performance among patient groups revealed that the LOAD was more profoundly impaired, in tasks of both spontaneous recall and semantic recognition. Voxel-Based Morphometry (VBM) analyses showed that impaired semantic performance in patients was associated with reduced gray matter volume in the anterior temporal lobe (ATL) region, while PET-FDG analyses revealed that poorer semantic performance was associated with greater hypometabolism in the left temporoparietal region, both areas reflecting key regions of the semantic network. Results of this study indicate that EOAD and LOAD patients present with distinct patterns of memory impairment, and that a genuine semantic impairment may represent one of the clinical hallmarks of LOAD.

Exome sequencing identifies 2 novel presenilin 1 mutations (p.L166V and p.S230R) in British early-onset Alzheimer's disease

Early-onset Alzheimer's disease (EOAD) represents 1%–2% of the Alzheimer's disease (AD) cases, and it is generally characterized by a positive family history and a rapidly progressive symptomatology. Rare coding and fully penetrant variants in amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) are the only causative mutations reported for autosomal dominant AD. Thus, in this study we used exome sequencing data to rapidly screen rare coding variability in APP, PSEN1, and PSEN2, in a British cohort composed of 47 unrelated EOAD cases and 179 elderly controls, neuropathologically proven. We report 2 novel and likely pathogenic variants in PSEN1 (p.L166V and p.S230R). A comprehensive catalog of rare pathogenic variants in the AD Mendelian genes is pivotal for a premortem diagnosis of autosomal dominant EOAD and for the differential diagnosis with other early onset dementias such as frontotemporal dementia (FTD) and Creutzfeldt-Jakob disease (CJD).

Parkinsonism and distinct dementia patterns in a family with the MAPT R406W mutation

BACKGROUND

The Arg406Trp (R406W) missense mutation in the microtubule-associated protein-tau gene (MAPT) is a known cause of early-onset dementia. Various dementia phenotypes have been described, including frontotemporal dementia (FTD), FTD with parkinsonism, and early-onset Alzheimer disease (EOAD)-like presentations.

METHODS

Using whole-exome capture with subsequent sequencing, we identified the R406W mutation in a family with multiple individuals with clinically diagnosed EOAD, in a pattern suggesting autosomal dominant inheritance. We reevaluated all available family members clinically.

RESULTS

Each of the affected individuals had a course meeting clinical criteria for EOAD. Two distinct disease trajectories were apparent: one rapidly progressive, and the other long and gradual. Four of five affected individuals also manifested parkinsonian symptoms. FTD features were not prominent and, when present, appeared only late in the course of dementia.

CONCLUSIONS

The MAPT R406W mutation is associated with EOAD-like symptoms and parkinsonism without FTD, as well as distinct cognitive courses.

Clinical and molecular studies reveal a PSEN1 mutation (L153V) in a Peruvian family with early-onset Alzheimer's disease

Presenilin 1 (PSEN1) gene mutations are found in 30-70% of familial early-onset Alzheimer disease (EOAD) cases (onset <60 years). Prevalence of these mutations is highly variable including ethnic differences worldwide. No Peruvian kindred with familial AD (FAD) have been described. Standardized clinical evaluation and cognitive assessment were completed in a Peruvian family with severe EOAD. Clinical course was characterized by very early onset (before age 35 years), progressive cognitive impairment with early memory loss, spatial disorientation and executive dysfunction. We sequenced all exons of PSEN1 in the proband and identified a c.475C>G DNA change resulting in a p.L153V missense mutation in the transmembrane domain 2 of the gene. This mutation is also present in the three additional affected siblings but not in a non-affected family member consistent with segregation of this mutation with the disease. This is the first report of a Peruvian family affected with EOAD associated with a PSEN1 mutation. This same mutation has been reported previously in English and French families, but a novel variants very close to the mutation and ancestry informative markers analysis suggests the mutation might be of Amerindian or African origin in this Peruvian family.

White matter microstructural damage in Alzheimer's disease at different ages of onset

White matter (WM) microstructural damage and its relationship with cortical abnormalities were explored in early-onset Alzheimer's disease (EOAD) compared with late-onset AD (LOAD) patients. Structural and diffusion tensor magnetic resonance images were obtained from 22 EOAD patients, 35 LOAD patients, and 40 healthy controls. Patterns of WM microstructural damage and cortical atrophy, as well as their relationships, were assessed using tract-based spatial statistics, tractography and voxel-based morphometry. Compared with LOAD, EOAD patients had a more severe and distributed pattern of WM microstructural damage, in particular in the posterior fibers of cingulum and corpus callosum. In both groups with Alzheimer's disease, but especially in LOAD patients, correlations between cingulum and corpus callosum fractional anisotropy and parietal, temporal, and frontal cortical volumes were found. In conclusion, WM microstructural damage is more severe in EOAD compared with LOAD patients. Such damage follows different patterns of topographical distribution in the 2 patient groups.

Exercise and early-onset Alzheimer's disease: theoretical considerations

BACKGROUND/AIMS

Although studies show a negative relationship between physical activity and the risk for cognitive impairment and late-onset Alzheimer's disease, studies concerning early-onset Alzheimer's disease (EOAD) are lacking. This review aims to justify the value of exercise interventions in EOAD by providing theoretical considerations that include neurobiological processes.

METHODS

A literature search on key words related to early-onset dementia, exercise, imaging, neurobiological mechanisms, and cognitive reserve was performed.

RESULTS/CONCLUSION

Brain regions and neurobiological processes contributing to the positive effects of exercise are affected in EOAD and, thus, provide theoretical support for exercise interventions in EOAD. Finally, we present the design of a randomized controlled trial currently being conducted in early-onset dementia patients.

A Case of Biopsy-proven Early-onset Alzheimer's Disease with Hemiparkinsonism

Patients with dementia and concomitant parkinsonism are frequently encountered in the elderly population. When it comes to young adults, however, coexistence of Alzheimer's disease (AD) and Parkinson's disease (PD) is rare. We described a case of 47-year old man with presenile onset dementia associated with hemiparkinsonism involving the right extremities. Brain biopsy showed neurofibrillary tangles and neuritic plaques, compatible with Alzheimer's disease. Iodine-123 labelled N-(3-iodopropen-2-yl)-2beta-carbomethoxy-3beta-(4-chlorophenyl) tropane ([(123)I]IPT) SPECT, dopamine transporter imaging, revealed a decreased uptake in both basal ganglia, more severe on the left side, particularly the caudal putamen, which is consistent with the finding of idiopathic Parkinson's disease. This case is unique in that damage on the nigrostriatal dopaminergic system in a patient with Alzheimer's disease was demonstrated by a functional neuroimaging study and that early-onset AD and early-onset PD, two rare conditions, coexist in the same individual.