Factsheet
Condition:
Alzheimer disease
Inheritance:
Multifactorial; rare autosomal dominant forms exist.
Genetic Etiology:
Autosomal dominant disorders due to mutations in PSEN1, APP, or PSEN2 genes, encoding presenilin-1, amyloid beta A4 protein, and presenilin-2, respectively. Otherwise etiology is multifactorial, with e 4 allele at APOE locus representing a risk factor.
Frequency:
Upwards of 5% of individuals over 70 years of age have signs of Alzheimer disease. Less than 2% of cases are due to single gene mutations.
Clinical features:
Alzheimer disease presents with memory loss and confusion, and may include language problems, poor judgment, agitation, and hallucinations. Brain atrophy is seen by MRI. There are no physical signs of the disease.
Management:
Supportive care.
Genetic counseling:
First-degree relatives face 20–25% risk of developing Alzheimer disease; rare single gene causes display autosomal dominant inheritance.