Background/Purpose: AA amyloidosis (AAA) is a rare, systemic form of amyloidosis, which mostly occurs secondary to chronic inflammatory conditions, predominantly systemic arthritides. AAA is characterized by abnormal deposition of amyloid A proteins, which can be deposited in a variety of organs, most often the kidneys. While there is currently no approved treatment for AAA, treatment of the inflammation can reduce manifestations of AAA in some patients¹. As with most rare diseases, understanding the epidemiology and prevalence of the disease is difficult, but is critical to improving the ability to diagnose the disease in a timely manner such that optimal treatment can be provided to patients². As there is no clear source that defines the prevalence of AAA, we sought to evaluate prevalence in the US and EU5.

Methods: Five different methodologies were evaluated for use in the estimation of prevalence of AAA, three of which were chosen as robust approaches for regionally specific estimations. The methodologies used included: 1) Evaluation of AAA diagnosis rate via renal biopsy with extrapolation to that regional population based on overall rate of renal biopsy, 2) Assessment of multiple regional centers of excellence with patient registries or databases, with extrapolation to those regional populations, and 3) A survey of 270 US physicians, including nephrologists, rheumatologists, and gastroenterologists, to assess numbers and rates of AAA patient diagnoses.

Results: Estimates suggest that there are 9,100-15,500 AAA patients currently under the care of a physician in the US and approximately 6,200 patients in the EU5. Data reveal that 40-68% of the primary conditions in AAA patients are arthritic in nature, and suggest that US rheumatologists are managing close to 30% of AAA patients. Approximately half of US rheumatologists are currently managing AAA patients. Rheumatologists are generally more aware than other specialists of the signs of AAA, the first sign of which is typically the development of kidney disease. Patients are then referred to a nephrologist for confirmation of the diagnosis, which is most often done by renal biopsy. Compared to the US, care in the EU5 is more highly centralized and patients are often referred to an AAA center of excellence.

Conclusion: Understanding the prevalence of a rare disease is typically difficult due in large part to the small numbers of patients spread out across the globe. Other reasons are low awareness of the disease and regional variations in clinical practice. In addition, global registries are not in place for most rare diseases. This research suggests an AAA prevalence of 9,100-15,500 patients in the US and approximately 6,200 in the EU5. In the US, rheumatologists are managing a large portion of the patients. Bringing together centers of excellence and thought leaders to develop a global patient registry would help to further define the epidemiology and prevalence of AAA, and increase awareness of this rare but devastating disease. References: ¹Dember LM. Amyloidosis-associated kidney disease. J Am Soc Nephrol 2006;17:3458-3471. ²Lachmann HJ et al. Natural history and outcome in systemic AA Amyloidosis. NEJM 2007;356:2361-71.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/aa-amyloidosis-an-evaluation-of-epidemiology-and-prevalence-in-the-us-and-eu5-countries/