Transmission of Alzheimer’s Disease: Evidence from Long-Term Follow-up of Human Growth Hormone Recipients

A recent article in Nature Medicine reports groundbreaking evidence suggesting that Alzheimer’s disease (AD) can be transmitted from person to person, based on the long-term follow-up of patients who received human growth hormone (hGH) derived from brain tissue of deceased donors. The study unveils a potential environmental route for acquiring AD, alongside its sporadic and inherited forms, and raises implications for revisiting preventive measures to avoid accidental transmissions through medical and surgical procedures.

Key Findings and Context:

1. Iatrogenic Transmission of AD: The study focuses on patients who received hGH derived from cadaveric pituitary glands, a practice that took place until 1985. The recipients of cadaver-derived hGH were exposed to potential contamination with amyloid-beta (Aβ) seeds, abnormal proteins associated with AD.
2. Parallel with Creutzfeldt–Jakob Disease (CJD): The transmission of AD mirrors the previously reported iatrogenic transmission of Creutzfeldt–Jakob disease (CJD) in patients who received the same contaminated hGH preparations. Both AD and CJD involve abnormal protein aggregates—Aβ in AD and prions in CJD.
3. Five Cases of Early-Onset Alzheimer’s: The study identifies five recipients of cadaver-derived hGH who developed early-onset Alzheimer’s disease. This provides the first evidence of human-to-human transmission of AD.
4. Similarities with Prion Diseases: The study suggests that propagating Aβ assemblies may exhibit structural diversity akin to conventional prions, leading to the possibility of therapeutic strategies targeting disease-related assemblies.
5. Implications for Preventive Measures: While iatrogenic transmission of AD is considered rare, the findings prompt a reevaluation of preventive measures to mitigate the risk of accidental transmissions through medical and surgical procedures.
6. Long Lag Time: Given the lengthy period between exposure to contaminated hGH and the development of clinical AD, the study highlights the importance of recognizing this potential risk even decades after exposure.
7. Need for Further Research: The study contributes to the understanding of AD’s environmental forms and emphasizes the importance of ongoing research to explore dynamics, therapeutic implications, and preventive strategies.

Conclusion:

The Nature Medicine article presents a paradigm-shifting perspective on the transmission of Alzheimer’s disease, shedding light on iatrogenic forms alongside sporadic and inherited cases. The study underscores the need for continued investigation into the environmental factors influencing AD and provides valuable insights for future research, diagnostic approaches, and preventive measures.