Iatrogenic Alzheimer’s disease Shows Typical AD Pathology with Prominent Language Impairment: JAMA

A new study published in the Journal of the American Medical Association revealed that patients with iatrogenic Alzheimer’s disease (iAD) can exhibit histopathological features similar to sporadic Alzheimer’s disease, with notable language impairment emerging as a key clinical characteristic of this subtype.

This case series have documented four men who developed what is now being termed iatrogenic Alzheimer disease (iAD) which is associated with exposure to contaminated medical products. All four individuals had received cadaveric pituitary–derived human growth hormone (c-hGH) during childhood, a treatment used decades ago before synthetic alternatives became available.

Based on patients referred to the UK National Prion Clinic between 2024 and 2025, this study suggests that these treatments may have inadvertently introduced amyloid-β (Aβ) “seeds” into the brain. These seeds are known to play a crucial role in Alzheimer disease by promoting the buildup of amyloid plaques.

What made these findings particularly significant were the growing evidence that Aβ pathology may spread in a “prion-like” manner, where misfolded proteins can trigger similar misfolding in healthy proteins, which propagates the disease over time. This mechanism has previously been linked to iatrogenic cerebral amyloid angiopathy, but its role in full Alzheimer disease has only recently come into focus.

The four patients described in the report developed symptoms between the ages of 47 and 60, which was earlier than is typical for sporadic Alzheimer disease. Also, their cognitive decline was marked by prominent language impairments, rather than the more commonly recognized memory loss seen in most Alzheimer cases.

One patient, who began showing symptoms at age 47 and died at 57 and underwent a postmortem brain examination. The analysis revealed extensive amyloid plaque deposition and severe tau pathology inside neurons.

The other three patients exhibited similar clinical patterns, particularly difficulties with language, illuminating that this may be a distinguishing feature of iatrogenic Alzheimer disease. This findings could help clinicians identify and differentiate iAD from more typical forms of the condition.

Despite the use of c-hGH was discontinued decades ago, the long incubation period observed in these cases highlights the long lasting impact of past medical practices. It also raises queries on how protein-based pathologies may be transmitted and develop over time.

The findings of this series press on the need for continued vigilance in medical procedures and a deeper understanding of how neurodegenerative diseases can arise. Overall, the study reinforces that iatrogenic Alzheimer disease mirrors the biological characteristics of sporadic Alzheimer’s, while potentially presenting with language impairments.

Reference:

Banerjee, G., Mok, T. H., Hyare, H., Cousins, O., Jaunmuktane, Z., Mead, S., & Collinge, J. (2026). High-Level Alzheimer disease neuropathological change following iatrogenic exposure. JAMA Neurology. https://doi.org/10.1001/jamaneurol.2026.0437