Dear Editor, Takayasu arteritis (TAK) is a rare inflammatory condition of the large blood vessels that affects the aorta and its branches. Young females of Asian descent are typically the most affected by this disease, however, in the United States, most patients with TAK are white (1,2). Data regarding the epidemiology of TAK is limited; with most studies of the incidence and prevalence of the disease coming from Japan, where TAK is more prevalent.
The described incidence rate of TAK ranges from 0.3 to 3.3 per million per year and the prevalence ranges from 4.7 to 360 cases per million (3). Only two studies have evaluated the epidemiology of TAK in the United States; one of them demonstrated an incidence rate of 2.6 cases per million per year in Olmsted County, MN (4) and the other study described a prevalence of 0.9 cases per million in New York, which is the lowest prevalence reported to date (5).
This study was performed with the objective of estimating the epidemiology of Takayasu arteritis in Olmsted and 26 surrounding counties.
The study was conducted using the extended Rochester Epidemiology Project (REP) (6). The protocol was approved by the Mayo Clinic and Olmsted Medical Center Institutional Review Boards. Records from patients residing in Olmsted and surrounding 26 counties and with a diagnosis of TAK between January 1st, 2010, and December 31st, 2018 were individually reviewed to confirm the diagnosis of TAK. Patients that met the 1990 American College of Rheumatology criteria for TAK were included. Patients who denied use of their medical records for research were excluded. Point prevalence was calculated on January 1st, 2015 using the number of cases as the numerator and population counts from the REP census as the denominator. Prevalence rates were age- and sex-adjusted to the United States White 2010 population. Confidence intervals (CI) were computed by assuming that the number of prevalent cases followed a Poisson distribution.
Between January 1st, 2010 and December 31st, 2018 forty patients were identified on initial screen by diagnosis code and underwent comprehensive medical record review. One incident case and five prevalent cases of TAK, meeting ACR criteria, were included in the study.
As there was one incident case, the incidence rate could not be determined. With the five prevalent cases, a point prevalence was calculated on January 1st, 2015 establishing a prevalence of TAK of 8.4 per million population (95% CI: 1–15.8) in this population. The prevalence was higher in females (13 per million population; 95% CI: 0.2–26.2) compared with male patients (3.6 per million population; 95% CI: 0–10.7).
The prevalent cases included four females and one male. Four patients were white and one Asian. The mean age at diagnosis was 20.5 years (SD 4.5). Four patients had a vascular distribution of involvement classified as HATA type V and one HATA type I. As part of their treatment, all the patients received glucocorticoids, two methotrexate, two infliximab, two adalimumab and one azathioprine at any given time. Four of the patients required vascular interventions as part of their management.
In the present population-based study conducted in the Midwestern USA, the estimated prevalence of TAK was found to be 8.4 per million population. This is similar to the findings of other epidemiology studies outside of Asia that report a prevalence in the range of 4.7 to 25.2 per million population(3). Additionally, we found a higher prevalence in female patients, consistent with the reported female predominance of this disease. The majority of patients in our study were white, reflecting the demographic distribution of residents of Olmsted and surrounding counties.
The strengths of our study include the expanded REP, which is a unique record linkage system in Southern Minnesota and Western Wisconsin, allowing full access to the medical records of the studied patients. The limitations of our study, inherent to a retrospective study design, were the information is entirely dependent on what is reported on the medical records.
Understanding the epidemiology of TAK is essential for the advancement of research in this challenging disease.
Key Message:
The prevalence of Takayasu arteritis in the upper midwestern USA is 8.4 per million.
Funding Sources:
This study was made possible by through use of the resources of the Rochester Epidemiology Project, which is supported by the National Institute on Aging of the National Institutes of Health under Award Number R01AG034676, and Grant Number UL1 TR002377 from the National Center for Advancing Translational Sciences (NCATS), a component of the National Institutes of Health. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Footnotes
Conflict of interest: None
Ethics statement: We have received ethics board approval from Mayo Clinic IRB # 09-004685 and Olmsted Medical Center IRB # 025-OMC-19.
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