Assessment of Mendelian and risk-factor genes in Alzheimer disease: A prospective nationwide clinical utility study and recommendations for genetic screening

PURPOSE

To assess the likely pathogenic/pathogenic (LP/P) variants rates in Mendelian dementia genes and the moderate-to-strong risk factors rates in patients with Alzheimer disease (AD).

METHODS

We included 700 patients in a prospective study and performed exome sequencing. A panel of 28 Mendelian and 6 risk-factor genes was interpreted and returned to patients. We built a framework for risk variant interpretation and risk gradation and assessed the detection rates among early-onset AD (EOAD, age of onset (AOO) ≤65 years, n = 608) depending on AOO and pedigree structure and late-onset AD (66 < AOO < 75, n = 92).

RESULTS

Twenty-one patients carried a LP/P variant in a Mendelian gene (all with EOAD, 3.4%), 20 of 21 affected APP, PSEN1, or PSEN2. LP/P variant detection rates in EOAD ranged from 1.7% to 11.6% based on AOO and pedigree structure. Risk factors were found in 69.5% of the remaining 679 patients, including 83 (12.2%) being heterozygotes for rare risk variants, in decreasing order of frequency, in TREM2, ABCA7, ATP8B4, SORL1, and ABCA1, including 5 heterozygotes for multiple rare risk variants, suggesting non-monogenic inheritance, even in some autosomal-dominant-like pedigrees.

CONCLUSION

We suggest that genetic screening should be proposed to all EOAD patients and should no longer be prioritized based on pedigree structure.

Taking the A Train? Limited Consistency of Aβ42 and the Aβ42/40 Ratio in the AT(N) Classification

The consistency of cerebrospinal fluid amyloid-β (Aβ)42/40 ratio and Aβ 42 has not been assessed in the AT(N) classification system. We analyzed the classification changes of the dichotomized amyloid status (A+/A-) in 363 patients tested for Alzheimer's disease biomarkers after Aβ 42 was superseded by the Aβ 42/40 ratio. The consistency of Aβ 42 and the Aβ 42/40 ratio was very low. Notably, the proportions of "false" A+T-patients were considerable (74-91%) and corresponded mostly to patients not clinically diagnosed with Alzheimer's disease. Our results suggest that the interchangeability of Aβ 42/40 ratio and Aβ 42 is limited for classifying patients in clinical setting using the AT(N) scheme.

The role of neuropsychological assessment in adults with attention deficit/hyperactivity disorders

Attention-Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterized by inattention, hyperactivity and/or impulsivity. While ADHD was initially recognized as a childhood syndrome, scientific evidence accumulated to indicate that a significant proportion of ADHD children continue to experience symptoms of ADHD in adulthood. Moreover, the question of ADHD diagnosis can arise in adult patients who were not diagnosed in childhood. Currently, the diagnosis of ADHD in adulthood is based on the revised criteria described for children. However, their application for adults may be difficult for many reasons including compensation and comorbid disorders. To date, no clinical, neuropsychological, biological or imaging marker is available for the diagnosis of ADHD. Considering that ADHD is based on a neuropsychological model, in this article we will examine the usefulness of neuropsychological testing in the diagnosis in adults. We will first present diagnostic criteria of ADHD and the limits of their application in adults. We will then detail the neuropsychological data available in adult ADHD and the French and international clinical recommendations for neuropsychological assessment. Finally, we will explore the predictive value of neuropsychological scores in the diagnosis of ADHD and discuss key methodological points and perspectives for clinical research.