A little-known condition may be responsible for a large proportion of heart attacks or strokes among individuals with few or no conventional risk factors—and currently, no treatment is available, Gina Kolata writes for the New York Times.
Stumbling upon a disease
According to the New York Times, doctors for years have been perplexed by why otherwise healthy patients with no family history of cardiovascular disease suffer strokes or heart attacks.
Researchers in recent years have uncovered part of the answer while examining genetic studies for diseases and disorders such as leukemia and schizophrenia. They discovered that an accumulation of mutated stem cells in an individual's bone marrow raises the risk of death within a decade by 40% or 50%, particularly from a heart attack or stroke. Those mutated stem cells, which produce white blood cells that carry the same mutation, can over time replace normal stem cells and the normal white blood cells they produce.
The condition, called clonal hematopoiesis of potential (CHIP), appears to become more common with age. According to the Times, up to 20% of people in their 60s have CHIP, and that percentage jumps to 50% among individuals in their 80s. Researchers say the condition is not inherited and may be caused by chance or by exposure to toxins such as cigarette smoke, the Times reports.
The condition is not always fatal: The Times cites a case involving a 115-year old woman whose bone marrow was almost entirely overrun by mutated white blood cells. The woman ultimately died of a tumor, the Times reports.
However, the condition is now considered a significant a risk factor for heart attack or stroke—but unlike other risk factors, such as high bad cholesterol or high blood pressure, there currently is no treatment for CHIP, according to the Times.
According to the Times, physicians currently advise against testing for CHIP because there is no way to treat the condition or lessen its associated risks. Most CHIP cases are diagnosed accidentally when patients undergo genetic tests for other reasons. Individuals can choose to have a blood test for CHIP, but their health insurance might not cover the test, which can cost thousands of dollars.
For those who are diagnosed with CHIP, the awareness of their increased risk for heart attack or stroke can be "life-changing," the Times reports.
Brian Gear, a patient who was diagnosed with CHIP after undergoing genetic testing for an inherited blood cancer, said, "It is almost like a Ph.D. in letting go of control. ... As much as you want to have a plan and a destiny, you also have this thing. It's scary and it's terrifying." He added, "I don't want to use the word time-bomb, but that's how it feels."
Possible links to other diseases
The mysteries surrounding CHIP have prompted many medical researchers to refocus their studies. Peter Libby, a cardiologist at Brigham and Women's Hospital and professor of medicine at Harvard Medical School, said, "I'm turning part of my lab to work on this full time," adding, "It's really exciting."
Some researchers have uncovered early evidence linking CHIP with other conditions.
Benjamin Ebert, chair of medical oncology at the Dana-Farber Cancer Institute, and Kenneth Walsh, who directs University of Virginia School of Medicine's hematovascular biology center, found that mice implanted with stem cells containing the CHIP mutation developed plaques that led to inflammation. Ebert said, "For decades people have worked on inflammation as a cause of atherosclerosis, but it was not clear what initiated the inflammation." Ebert said CHIP might explain atherosclerosis and other inflammatory diseases, such as arthritis (Kolata, New York Times, 1/29).
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