High-Level Alzheimer Disease Neuropathological Change Following Iatrogenic Exposure.

Importance: Alzheimer disease (AD) is pathologically characterized by the deposition of amyloid-β (Aβ) and hyperphosphorylated tau. Human transmission of Aβ pathology in a prion-like fashion has resulted in iatrogenic cerebral amyloid angiopathy. More recently, iatrogenic Alzheimer disease (iAD) was described in recipients of cadaveric pituitary-derived human growth hormone (c-hGH) contaminated with Aβ amyloid seeds. Objective: To describe the clinical and postmortem findings in iAD. Design, Setting, and Participants: This case series describes 4 c-hGH recipients who were referred to the UK National Prion Clinic. Between February 2024 and February 2025, 14 c-hGH recipients had been referred to this service, with clinical assessments ongoing. The current study included 4 of 14 people treated with c-hGH who were referred since the original report. These data were analyzed during February and March 2025. Exposure: c-hGH contaminated with Aβ amyloid seeds. Main Outcomes and Measures: Clinical and histopathological description. Results: The study describes 4 males who developed dementia following confirmed or suspected c-hGH treatment in childhood (age at symptom onset between 47 and 60 years) with cognitive syndromes characterized by prominent language involvement. Results include clinical and postmortem findings for 1 patient (onset at age 47 years) in whom postmortem examination (at age 57 years) showed unequivocal neuropathological features of AD, including severe tauopathy. Brief descriptions of 3 additional patients with prominent language involvement are also provided. Conclusions and Relevance: These results demonstrate that patients with iAD can have histopathological findings classically found in sporadic AD and that prominent language involvement might be an important phenotypic feature in this AD subtype.