Steven Needell / Science Source
The history and findings in this case are suggestive of late-onset familial AD (onset after age 65 years).
AD is a common neurodegenerative disease associated with progressive impairment of behavioral and cognitive functions, including memory, comprehension, language, attention, reasoning, and judgment. In 2020, 5.8 million Americans were living with AD. By 2050, this number is projected to increase to 13.9 million people, or almost 3.3% of the US population. Globally, 152 million people are projected to have AD and other dementias by 2050. The worldwide increase in incidence and prevalence of AD is at least partially explained by an aging population and increased life expectancy.
The cause of AD remains unclear, but there is substantial evidence that AD is a highly heritable disorder. Familial AD is characterized by having more than one member in more than one generation with AD. The autosomal-dominant form of AD is linked to mutations in three genes: AAP on chromosome 21, PSEN1 on chromosome 14, and PSEN2 on chromosome 1. APP mutations may cause increased generation and aggregation of beta-amyloid peptide, whereas PSEN1 and PSEN2 mutations result in aggregation of beta-amyloid by interfering with the processing of gamma-secretase.
APOE is another genetic marker that increases the risk for AD. Isoform e4 of the APOE gene (located on chromosome 19) has been associated with more sporadic and familial forms of AD that present after age 65 years. Approximately 50% of individuals carrying one APOEe4 develop AD, and 90% of individuals who have two alleles develop AD. Variants in the gene for the sortilin receptor, SORT1, have also been found in familial and sporadic forms of AD.
The cognitive and behavioral impairment associated with AD significantly affects a patient's social and occupational functioning. Insidiously progressive memory loss is a characteristic symptoms seen in patients presenting with AD. As the disease advances over the course of several years, other areas of cognition are impaired. Patients may develop language disorders (eg, anomic aphasia or anomia) and impairment in visuospatial skills and executive functions. A slow progression of behavioral changes may also occur in individuals with AD.
Clinical criteria for the diagnosis of AD (eg, insidious onset of cognitive impairment, clear history of worsening symptoms) have been developed and are often used to diagnose patients. In addition, biomarker evidence may help to increase the diagnostic certainty. Several cerebrospinal fluid and blood biomarkers have shown excellent diagnostic ability by identifying tau pathology and cerebral amyloid-beta for AD.
Neuroimaging is becoming increasingly important for identifying the underlying causes of cognitive impairment. Currently, MRI is considered the preferred neuroimaging modality for AD because it allows for accurate measurement of the three-dimensional volume of brain structures, particularly the size of the hippocampus and related regions. CT can be used when MRI is not available or is contraindicated, such as in a patient with a pacemaker. PET is another noninvasive method for depicting tau pathology deposition and distribution in patients with cognitive impairment. In 2020, US Food and Drug Administration approved the first tau PET tracer, 18F-flortaucipir, which marked a significant achievement to improve AD diagnosis.
At present, the only therapies available for AD are symptomatic therapies. Cholinesterase inhibitors and a partial N-methyl-D-aspartate antagonist are the standard medical treatments for AD. Antiamyloid therapies are also available for patients with mild cognitive impairment or mild dementia. These include aducanumab, a first-in-class amyloid-beta–directed antibody that was approved in 2021, and lecanemab, another amyloid-beta–directed antibody that was approved in 2023. Both aducanumab and lecanemab are recommended for the treatment of patients with mild cognitive impairment or mild dementia stage of disease, the population in which the safety and efficacy of these newer agents were demonstrated in clinical trials.
Secondary symptoms of AD, such as depression, agitation, aggression, hallucinations, delusions, and/or sleep disorders, can be treated with psychotropic agents. Behavioral interventions including patient-centered approaches and caregiver training can also be helpful for managing the cognitive and behavioral manifestations of AD, often in combination with pharmacologic interventions (eg, anxiolytics for anxiety and agitation, neuroleptics for delusions or hallucinations, and antidepressants or mood stabilizers for mood disorders). Regular physical activity and exercise may also play a role in delaying AD progression and possibly conferring a protective effect on brain health.
Jasvinder Chawla, MD, Professor of Neurology, Loyola University Medical Center, Maywood; Director, Clinical Neurophysiology Lab, Department of Neurology, Hines VA Hospital, Hines, IL.
Jasvinder Chawla, MD, has disclosed no relevant financial relationships.
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