Epidemiology of hereditary transthyretin amyloidosis in the northernmost region of Sweden: a retrospective cohort study

Abstract

Introduction

Epidemiological data on hereditary transthyretin (ATTRv) amyloidosis from the northernmost region of Sweden (Norrbotten) are sparse.

Methods

We reviewed the medical records of all incident cases of ATTRv amyloidosis in Norrbotten between 2006 and 2018. Official population and mortality statistics were used to estimate incidence rates and standardised mortality ratios (SMRs).

Results

Ninety-three patients were diagnosed with ATTRv amyloidosis between 2006 and 2018 (median age, 72.8 years; 68.8% men; 95.7% Val30Met [p.Val50Met] mutation). The incidence rate per 100,000 persons and year increased from 1.50 (95% confidence interval [CI], 0.84–2.47) cases in 2006–2009 to 4.92 (95%CI, 3.46–6.78) cases in 2016–2018. The SMR in the ATTRv amyloidosis cohort was 2.64 times higher than in the general population in 2006–2018 (95%CI, 1.78–3.77). However, there were indications of lower SMRs over time (2006–2012, 2.96 [95%CI, 1.73–4.74]; 2013–2018, 2.32 [95%CI, 1.23–3.96]) and by use of disease-modifying drugs (no, 3.21 [95%CI, 1.87–5.13]; yes, 2.09 [95%CI, 1.08–3.64]).

Conclusion

The incidence of ATTRv amyloidosis increased 3-fold in Norrbotten between 2006 and 2018, most likely due to a previous underdiagnosis – with suggestions of lowered mortality during later years, possibly due to the introduction of disease-modifying drugs.

Keywords:

• Amyloid
• amyloidosis
• hereditary
• transthyretin
• epidemiology
• Sweden

Acknowledgments

The team specialized in ATTRv amyloidosis at the Department of Internal Medicine and Rehabilitation, Piteå Hospital, was initiated by Kenneth Lång and is currently headed by Jorge Mejia Baranda and Katarzyna Liszewska.

Author contributions

The authors’ responsibilities were as follows – Jorge Mejia Baranda and Jenny Ljungberg; acquired the data; Viktor Oskarsson: performed the statistical analyses; Jorge Mejia Baranda, Jenny Ljungberg, and Viktor Oskarsson: drafted the manuscript; and Jorge Mejia Baranda and Viktor Oskarsson: primary responsible for the final content. All authors interpreted the results, reviewed and revised the manuscript, approved the final version of the manuscript, and participated in the study design.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data described in the manuscript will not be made available to the public because of restrictions in the ethical approval.

Additional information

Funding

The current study was supported by grants from the Piteå Älvdals Hospital Foundation (Jorge Mejia Baranda and Viktor Oskarsson) and the Norrbotten County Council (Viktor Oskarsson).