Heterozygous amyloid precursor protein (APP) mutations cause hereditary cerebral amyloid angiopathy (CAA) and autosomal dominant Alzheimer's disease (AD). This study aimed at reporting an APP mutation and its associated clinical and neuroimaging features. The proband and her family members presented with memory loss, psychiatric, and visual symptoms. Neuroimaging revealed bilateral white matter intensities (WMH) in cranial magnetic resonance imaging (MRI), cortical calcification, and brain atrophy. Next-generation sequencing-based comprehensive gene panel revealed heterozygous missense variant c.2059A>C (p.K687Q) mutation in the APP gene. Co-segregation analysis identified seven family members to be APP mutation carriers while normal neuroimaging features were seen in all family members lacking the APP mutation. WMH and cortical calcification were observed in patients with CAA, including those with the Iowa (D694N) and Italian (E693K) mutations. Further studies should investigate the functional changes associated with the heterozygous APP mutation (K687Q).
Keywords: Alzheimer’s disease; Amyloid precursor protein; Cerebral amyloid angiopathy; Cortical calcification; K687Q; White matter intensities.