A medical mystery is still unfolding at the White House.
President Bush, like his wife, Barbara, has received a diagnosis of Graves' disease, an autoimmune ailment of unknown cause. It is rare enough for a husband and wife to contract the disease, which is not known to be communicable. Even odder is that Millie, the Bushes' dog, also has an autoimmune disease, one known as lupus.
The President's disease was diagnosed this month, the First Lady's in January 1990, and Millie's last summer. So in a span of 16 months, three members of the Bush household have contracted a disease in which the immune system, for unknown reasons, interferes with the body's own tissues.
The cluster of cases, of course, may be pure coincidence. But could whatever caused Millie's lupus also have induced the Graves' disease that has afflicted Mr. Bush and his wife? That is a possibility that has intrigued medical experts around the country, and it is now being considered by the President's physician, Dr. Burton J. Lee 3d.
Scientists have long suspected that microbes or other environmental factors might set off autoimmune disorders like lupus and Graves' disease among the individuals, human or animal, who are genetically susceptible. Among the current suspects is a bacterium known as Yersinia enterocolitica and the entities known as retroviruses, but nothing has been proved regarding either.
Could such an agent lurk either in the White House or the former Naval Observatory where the Bushes lived for the eight years, from 1981 to 1989, when Mr. Bush was Vice President? The following facts are the clues that may bear on this surmise.
Last summer, three and a half years after she joined the Bush household, Millie, a springer spaniel who has been the subject of a best-selling book, developed what was later diagnosed as lupus. The uncommon disorder of humans and dogs can cause a butterfly-shaped rash on the face, anemia, arthritis and kidney damage. Lupus is considered a classic model of an autoimmune disease.
Millie's malady has been treated with a steroid drug, prednisone, said Dr. Lee. "She was given a bad prognosis, but now she is doing pretty well, off prednisone," he said.
As in humans, the cause of lupus in dogs is unknown, but environmental factors seem to be important. Although some reports have hinted at links between lupus in families and in their household pets, documented transmission from dogs to humans is lacking.
Graves' disease is another classic autoimmune disorder. It causes the thyroid gland in the neck to produce too much of the hormone that controls the body's metabolism.
Graves' disease is much more common in women than men for reasons that remain uncertain. The Bushes' doctors have called the coincidence bizarre and have cited chances of one in three million that a husband and wife will develop Graves' disease. Other experts, like Dr. Paul W. Ladenson, at Johns Hopkins Hospital in Baltimore, have come up with an estimate of one in 100,000.
The coincidence has been a prime topic of discussion among leading thyroid experts and other doctors around the country, including those treating the Bushes. Only two thyroid experts among a dozen interviewed said they had ever diagnosed Graves' disease in a couple.
Vice President Dan Quayle and his wife, Marilyn, too, have wondered whether the Graves' disease that struck the Bushes might somehow be linked to "the ancient state of the plumbing and lead pipes" in the Vice Presidential residence, according to David C. Beckwith, Mr. Quayle's press secretary.
The Quayles' concern about the pipes apparently stems from the lead poisoning that veterinarians diagnosed in Millie before they determined last September that she had lupus. But the water supply may be checked anyway.
The Quayles have not been examined for a thyroid problem, Dr. Lee said, adding that finding such a problem "would be just an incredible coincidence."
Dr. Lee said he has asked Dr. Charles L. Christian, head of medicine at the Hospital for Special Surgery in New York and an expert in autoimmune disorders, to look over the Bushes' medical records, as well as Millie's, to make sure nothing has been overlooked.
One focus of the search will be for a history of autoimmune disorders on each side of the Bush family. A son, Marvin Bush, has regional enteritis, an autoimmune disorder.
Clusters, the bunching of cases of a disease in humans and animals in time and location, are often purely coincidental but have also proved the clue to many significant medical advances.
From study of a cluster of birth defects Dr. Norman M. Gregg, an Australian physician, discovered in 1941 that the fetus was highly vulnerable to the virus that causes German measles. A cluster of cases of vaginal cancer in young women led doctors in Boston to blame the hormone DES, or diethylstilbesterol, that had been taken by their mothers during pregnancy.
But studies of clusters usually lead to dead ends, not least because many clusters turn out to be statistical flukes.
One cluster of overactive thyroids involved a group of endocrinologists at Mount Sinai Hospital in New York City in 1976. They wondered whether the condition might be an occupational hazard, but a team led by Dr. Robert L. Segal could find no common cause.
In recent years, researchers have reported finding tantalizing clues to retroviruses in Graves' disease, lupus and other autoimmune disorders. But the findings have not been confirmed.
Scientists also have renewed interest in the possible role of Yersinia enterocolitica in Graves' disease. A scientific journal, Autoimmunity, late last year published several articles on the subject.
An infectious agent has never seemed likely as the cause of Graves' disease because this and other autoimmune diseases do not strike the classic target of infections, like households, college dormitories, military barracks and schools.