Genetic Factor Emerges as Key to Onset of Lyme Arthritis
By LAWRENCE K. ALTMAN
Published: July 3, 1990
SCIENTISTS have discovered a hereditary factor that greatly increases susceptibility to the chronic arthritis that can change Lyme disease from an almost unnoticeable ailment to an affliction lasting several years.
The disabling arthritis is believed to develop in only about 10 percent of people whose bout with the disease is untreated. Almost all of them have the inherited factor, a component on the surface of white blood cells. Although this chronic arthritis can usually be prevented with the same antibiotics that can cure the arthritis in its initial stages, the drugs are often ineffective in the chronic phase, which can last for years.
Scientists do not know yet whether heart and neurological complications are also linked to inherited factors, but they believe the test for the hereditary factor may eventually open up new avenues to treating Lyme disease, the researchers who made the discovery said. For example, people with the factor might receive more intensive antibiotic treatment earlier.
The research is one of many studies on an increasingly troublesome ailment.
The findings may also contribute to one of the most intractable problems doctors face with Lyme disease - their inability to tell for sure who has the disease and who doesn't.
Lyme disease, named for a small town in Connecticut where an outbreak occurred in 1975, is caused by a kind of bacterium, the spirochete Borrelia burgdorferi, spread by tiny ticks. Most people bitten by the ticks develop a telltale rash with a bull's-eye pattern a week or so later; they may also suffer flu-like symptoms, like headache, mild fever, swollen lymph glands and malaise. But for many people the symptoms are mild, and some have no symptoms at all. Most people recover completely, but for others complications emerge years later.
The new findings on hereditary factors were reported at the fourth international meeting on Lyme disease in Stockholm recently by researchers from Tufts-New England Medical Center in Boston, the Hospital for Joint Diseases in New York and New York University.
Other research fronts are these:
* The Centers for Disease Control has begun studies to ascertain the accuracy of various commercial diagnostic tests.
* Health officials have devised a new list of findings, symptoms and laboratory tests as an epidemiological standard for doctors, who will be asked to report cases to local health departments in all states by next year.
* Entomologists are collecting data to prepare maps showing the distribution of the species of ticks that can carry the disease. Although most experts doubt that other insects are involved in Lyme disease, they are investigating the possibility.
* Researchers are also investigating the ways that the spirochete that causes Lyme disease acts in the body like its cousin, the spirochete that causes syphilis.
* They are also studying whether the spirochete varies from place to place. Such variation would explain the fact that arthritis is the most common complication in the United States, whereas in Europe neurological complications are more common.
Last year, the preliminary national total of cases voluntarily reported by physicians was 7,402. But researchers do not believe the number is reliable.
Surveillance for Lyme disease is incomplete, said Dr. Guthrie S. Birkhead 3d, whose team from the New York State Health Department studied hospital records and case reports of the disease. They found that some people with Lyme disease were going unreported while others were treated for a disease they did not have.
Of 2,735 cases with onset of illness in 1988, Dr. Birkhead said that 1,383 cases met the Centers for Disease Control's earlier definition of a confirmed case and 1,352 cases did not.
The Testing A Difficult Diagnosis
Although tests for antibodies to the spirochete showed evidence of infection in most of the unconfirmed cases, the researchers could not differentiate between people who had just come down with the disease and those who had the antibodies because they had such a mild case that it produced no symptoms or had the disease some time ago and recovered from it. To be sure, doctors generally need two blood specimens obtained weeks apart to document a rise in antibodies.
Of 303 patients admitted to hospitals for Lyme disease in New York in 1987, one-third met the case definition and only one-third of that number were reported.
''One reason for the discrepancy is the tendency to treat patients with uncertain symptoms to be on the safe side,'' Dr. Birkhead said. Another possible reason, he said, is that patients who believe they have Lyme disease will seek out a doctor who will confirm and treat it, even if they do not have it.
To improve the accuracy of reports and to keep better track of Lyme cases, Federal and state health officials are making Lyme a nationally reportable disease, effective next year.
''We want to be able to better map trends, get a better handle on what is really Lyme disease, and identify priorities for action,'' said Dr. David T. Dennis, a Lyme disease epidemiologist at the Center for Disease Control's laboratory in Fort Collins, Colo.