Ninety percent of people in the United States who have the chronic autoimmune disease lupus are women and, according to two new studies published recently in Arthritis & Rheumatology, large proportions are Hispanic or Asian. Like African-Americans, these two ethnic/racial groups are not only at higher risk of lupus than whites, they’re also more likely to have aggressive forms of the disease, researchers in New York and San Francisco found.
Lupus, or systemic lupus erythematosus (SLE), an affect virtually every organ system, and symptoms vary widely. Some patients have relatively mild skin and joint symptoms that may go into remission for long periods. Others have cognitive (neuropsychiatric) manifestations or life-threatening complications such as lung, heart and kidney problems.
In early September, singer Selena Gomez, 25, made headlines when she received a kidney transplant for lupus nephritis, a potentially life-threatening kidney inflammation caused by lupus. (Gomez reportedly has also been treated for depression, another common lupus symptom.)
Lupus’ complexity – the disease is often called “the great imitator” because it mimics many other diseases – and the fact that it’s relatively uncommon, have made it hard to estimate how many people are living with it. Some older studies suggest it affects anywhere from 161,000 to 322,000 people in the U.S.
The Centers for Disease Control and Prevention (CDC) wanted more credible statistics, so in 2004 it funded five population-based registries to help determine lupus rates across ethnic and racial populations in the U.S. The two just-released studies from registries in Manhattan and San Francisco are the latest in the series. They were specifically designed to estimate overall prevalence (the number of people who have it in a given time period) and incidence (the number of people newly diagnosed with it in a given time period) among Hispanics and Asians – groups for which data are lacking. (The first three studies published results on lupus’ prevalence and incidence in whites, blacks and American Indians/Native Alaskans.)
In the New York study (called the Manhattan Lupus Surveillance Program), researchers reviewed medical records to determine the number of people who had lupus in 2007 and the number of new cases diagnosed from 2007 to 2009. Although the exact percentages varied depending on the type of classification criteria used, the overall patterns were similar.
For instance, using American College of Rheumatology (ACR) criteria, the researchers found that nine times more women than men had or were newly diagnosed with lupus. They also found that, as in previous studies, African-American women had the highest rates (210.9 per 100,000 persons annually) compared with white women (64.3 persons annually). But Hispanics and Asians also had unusually high numbers: 138.3 and 91.2 per 100,000 persons annually, respectively. Incidence was more than twice as high in African-Americans as in the other three groups (15.7 vs. 6.5 persons annually).
Peter Izmirly, MD, assistant professor of medicine at NYU Langone Health in New York City, a specialist in lupus and lupus nephritis and lead author of the Manhattan study, says the results confirm “the clinical impressions that more non-whites have lupus than whites.”
And, he says, they have more aggressive disease. “Based on our data, 50 percent of non-white cases developed lupus nephritis, one of the most serious and disabling manifestations of the disease, compared with 25 percent of whites,” he says.
Maria Dall’Era, MD, lead author of the San Francisco study (The California Lupus Surveillance Project), directs the Lupus Center at the University of California, San Francisco. She says she and her colleagues found the same racial and ethnic disparities in the incidence and prevalence of lupus that the Manhattan researchers did.
No one is sure why lupus seems to target some groups more than others, although as with many autoimmune diseases, the most likely guess it that some combination of genes and environment plays a role, according to George Stojan, MD. Dr. Stojan is an assistant professor of medicine at the Johns Hopkins University School of Medicine in Baltimore and a member of the Lupus Center there, but wasn’t involved in the CDC registry studies.
He notes that the diverse populations in Manhattan and San Francisco have allowed researchers to see for the first time how lupus affects Hispanics and Asians and that this information has real value.
“These population-based studies underline the ethnic disparities in [lupus] and provide a valuable framework for further research into the genetic and environmental factors underlying these differences,” says Dr. Stojan.
In the shorter term, Dr. Izmirly says the studies should make health care providers more aware of lupus in these groups and consider the diagnosis in patients who have symptoms that suggest it, such as arthritis, rashes and early signs of kidney disease.
Author: Linda Rath for the Arthritis Foundation