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\"it was like a bowling ball hitting us in the face,\" said vicki. she was referring to the moment when she and her sisters learned that they may all have inherited a gene that could give them vhl, the disease that had killed their oldest sister lydia.
lydia had been sickly throughout her childhood. vicki, mary, and charlotte had been fine as kids. but in their thirties and shortly after they discovered that their sister'；s disease was hereditary, each sister developed some sign of the disease.
vhl is rare in the general population--probably seven thousand people in the united states have it. but, in this one family, the four sisters inherited the vhl gene as did three of their eight kids, and the sisters'； mother nellie has it as well. nellie is sure that her mother died of vhl, even though that diagnosis was never attached to her illness. and nellie'；s mother'；s father had died of a kind of cancer that is associated with the disease. so, even though vhl is not a common disease, for nellie'；s family and for other \"affected\" families, the disease is as common as the \"common cold.\"
nellie says she first heard of vhl when she was in her twenties. she was chasing one of her tiny daughters at a swimming pool, slipped, fell, hit her head, and was instantly and permanently blind in one eye. one doctor said the blindness was caused by the fall； another said it was caused by a rare condition called vhl. nellie says she heard no more about vhl for about thirty years. then, when lydia was hospitalized, the doctor said lydia had vhl.
nellie recalls how hard it was to return home from the hospital that day and tell her other daughters that lydia had a genetic disease and that they might all have it too. \"mama, please tell me i'；m adopted,\" said one of the daughters who was hoping against hope that her genes had come from someone else. the chance for each daughter to inherit the vhl gene was just 50:50, but, as they learned several years later, the gene had found its way into all of them.
vhl can be a mild disease or severe, an inconvenience to those who have it or a killer. tumors and cysts can develop in several areas of the body--the eyes, brain, spinal cord, kidneys, and a few other sites (1)--and patients'； symptoms reflect where the tumors and cysts are growing. some patients have headaches and a range of motor problems and pain because they have tumors in their brains； some experience vision problems or blindness as a result of eye tumors； some have kidney failure when tumors overtake that organ.
two turn-of-the-century eye doctors--von hippel in germany and lindau in sweden--were the first to publish descriptions of the vhl tumors in patients'； eyes and brains； in the 1960s the disease was named vhl, von hippel-lindau, to recognize their contributions in characterizing the disease (2). von hippel and lindau observed that these tumors ran in families (3), but it was not until 1993 that scientists actually identified and isolated the disease-causing gene (4). the search took six years and involved studies of genes from hundreds of people in 120 affected families. nellie, her daughters, and many of their relatives were among those who donated blood samples for this research.
dr. berton zbar, one of the discoverers of the gene, first met with nellie and her family in 1988. together they made a family tree that went back as far as the family could remember. it listed each relative'；s illnesses and any symptoms that might suggest vhl. zbar then collected 40 milliliters of blood from each of the 25 members of the family who had come together. these blood samples and samples from hundreds of other people in affected families were key to the identification of the vhl gene, which was tracked to the short arm of chromosome 3.
associating a gene with a disease is just the first step in a long and often slow process whos |
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发表于 2006-4-2 03:32
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发表于 2006-4-2 15:10
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