Blood Matters Read online

  The day had begun with a visit to Children’s Hospital in Hershey, a taxing forty miles from the clinic, to check on month-old Marlene with the colostomy bag and an IV drip of Morton’s special maple syrup disease formula. The maple syrup was not the problem: Both Marlene and Arlene had been diagnosed within forty-eight hours of birth, put on the special formula, and sent home. But then Marlene began to show signs of a bowel obstruction. She returned to the hospital, where she was diagnosed with Hirschsprung’s disease, another apparently recessive disorder. Babies with this condition lack normal nerve cells in a part of the intestine, which means stool is not moved forward, causing an obstruction to form. Surgeons had removed the part of the girl’s intestine that was missing the normal nerve cells—“about most of her left colon,” as Morton put it—and she was now recovering. Morton was pleased. He talked up the merits of her diet, too: “It’s actually an unusually good formula, because we made it,” he said and told me the story of working with a company called Applied Nutrition to design a food suitable for maple syrup babies and children, on the condition that the company would provide Lancaster County children with the formula free of charge for a period of time—and get data on their nutrient levels in return. Then he had one of those meaningful bedside conversations with the baby’s attending physician.

  “Looks like she just advanced on her feeds?” the country doctor asked.

  “Yep,” the man in hospital scrubs answered. “Doing all right?”

  “Yep.”

  “So how much faster do you want to advance her?”

  “Well, that was our question for you.”

  “Well, the goal is three ounces every three hours.”

  “All right.”

  With that, Morton gathered up his bulging pigskin briefcase and readied to go, but a group of doctors in scrubs stopped him to talk about an article that had just come out in Smithsonian magazine. Titled “Medical Sleuth,” it told the story of Morton’s investigation into the sudden death of an Amish infant. Her parents were charged with abuse, but he ultimately proved that the baby had died as a result of a genetic condition. This was the second article about Morton in a major national magazine in a couple of months: Long revered locally, he was now becoming a national entity, if not yet a celebrity.

  He led me to the elevator, where he lectured me on the management of maple syrup disease, down to the parking lot, where he expounded on the business of medicine—or rather, the way medicine had been turned into a business—and into the car, where he talked to me about the need for genetic testing for everything, the whole thirty-mile drive to Lancaster, Pennsylvania. We were on our way to Lancaster General Hospital to see the little girl’s older brother, thirteen-year-old Henry, who had been hospitalized thirty-six hours earlier with a maple syrup disease crisis. These children have episodic crises, often brought on by an otherwise innocuous viral infection that causes their metabolism to go out of whack. Morton’s treatment protocol prescribes a special “sick-day” diet for maple syrup children, but that does not always help. Their metabolism loses its mind, and so do they: Their brains swell.

  Henry’s father had been unable to wake the boy up, and when Henry did wake up, he had been absent. “When he came in the other night, he didn’t know who he was or where he was,” Morton explained. “Wasn’t particularly sick, he doesn’t have like pneumonia or gastroenteritis or anything, he just had an upset stomach and started vomiting, and how much of that was just due to the metabolic disease and how much was the underlying bug that provoked it, we don’t know, except it was a fairly ordinary illness that in another child might make him feel bad for a day or two but in these kids just sort of cycles into this state where they just can’t get themselves out of trouble. They can’t drink enough formula to get the lucene [an amino acid] level down. And basically, as they become fasted and ill, they begin to break down protein, which is part of the normal metabolic response to the illness, and their blood amino acid levels go up, or their lucene level goes up, and the higher the lucene level is, the more encephalopathic they become and the more they vomit, and it’s just sort of a vicious cycle.”

  There was a sickening, treacly smell in the boy’s room: It smelled of maple syrup, and this meant he was still in trouble. His lucene level had been 17 when he arrived. Per Morton’s standard instructions in these cases, the hospital had put Henry on a special IV solution that was pumping four thousand calories a day into his body, forcing his metabolism into overdrive, leading him to synthesize protein at a very high rate, restoring a normal balance. Within twenty-four hours, Henry’s lucene level had gone down to 13, and Morton was predicting it would be down to less than half that in another twenty-four hours, which would mean Henry could be weaned off the IV solution and return to his usual formula.

  Henry was a pale boy, very small for his age—one would expect that, with a diet that restricted him to sustenance levels of proteins—but otherwise he looked just like any child in a hospital room: simultaneously bored and pleased to be able to watch television all day long. “Gonna ruin you, watching that thing, you know,” said Morton, shoving his fist into the boy’s slightly distended stomach. “Does it hurt when I punch there? Is it sore? These guys get pancreatitis,” said Morton, turning to me now. “They always have this epigastric tenderness and vomiting, and it’s—we think the pancreas swells just like the brain does. It hurts down there and up there, and they just stop thinking straight. So,” he was facing down at Henry again. “You look a lot better.”

  Before leaving Henry’s room, Morton swirled a Q-tip in Henry’s ear. “What people don’t realize,” he explained, “is that the smell of maple syrup isn’t from the tree but from the bacteria. So when people come in, I tell them they can send an expensive test to the Mayo Clinic and wait two weeks or use a Q-tip and know.” Morton stuck the Q-tip under the nose of Corinne, a new nurse on the ward. Henry’s earwax smelled like maple syrup. “Henry can teach you all about MSUD,” he said.

  Henry could also teach her all about genetics. Henry’s parents were double first cousins—their mothers were sisters and their fathers were brothers—which meant that roughly 25 percent of the children’s genome was homozygous: Both copies of the gene were identical. Like most Mennonites, the couple had a lot of children, though Morton could not be sure how many exactly. “About eight, maybe nine,” he said slowly, as though struggling to remember. “There are a couple of kids I don’t know.” He had reason to know only the children who had any of the two or three genetic disorders that ran in the family.

  Four of their children were affected with maple syrup disease. They also had two children with SCID, severe combined immunodeficiency, or “bubble boy,” disease, a recessive disorder that handicaps the immune system, making children catastrophically vulnerable to all sorts of bacteria and viruses. Babies with untreated SCID rarely survive their infanthood, but treatment—including bone-marrow transplants—can allow them to develop normally. One of Henry’s siblings, affected with both SCID and MSUD, received a bone-marrow transplant, which not only cured the SCID but significantly lessened the symptoms of MSUD. “So there was another one of those little experiments you don’t get to do every day,” said Morton. The beneficial effect of a bone-marrow transplant on the symptoms of maple syrup disease is the sort of thing that would make for a nice article in a medical journal—“it tells you that bone-marrow transplant is a kind of gene therapy”—but Morton did not have the time to write articles about every one of his “little experiments.”

  Were he so inclined, Morton could mine the family for a good number of scientific reports. Three of the kids—including the newborn Marlene—had Hirschsprung’s disease. The intestinal disorder is believed to be what is called a complex trait, a condition caused by a combination of mutations in several different genes, with one mutation the main culprit, while specific variants of other genes act as modifiers, determining the severity of the condition. Three genes have been identified as the main culprits in different popul
ations: RET, EDNRB, and EDN3. It was a mutation in EDNRB that was believed to cause Hirschsprung’s in the Mennonite population. Back in the mid-1990s, when few disease-causing mutations were known by name, a geneticist named Erik Puffenberger wrote his doctoral dissertation on this gene and its role in causing Hirschsprung’s among the Mennonites. But here was the thing. Baby Marlene’s two older siblings with the disease carried the mutation described by Puffenberger, but Marlene did not. And, said Morton, she seemed to be homozygous for an area of the RET gene, suggesting that might be the cause of her Hirschsprung’s, which, in turn, suggested two things: that the unlucky parents were actually both carriers of two separate mutations that caused Hirschsprung’s; and that, more generally, both of these mutations were found in the Mennonite population. “This is cause for him to redo his Ph.D.,” chuckled Morton.

  ***

  If Morton looked like what a country doctor should look like, then Erik Puffenberger looked like what a scientist should look like. Not the absentminded professor type, but the young, anal, collected type, the type to whom you would entrust the mapping of your child’s genome. One look at Puffenberger told you this was a man who was never late, never forgetful, who would never spill one drop of fluorescent marking solution or misplace a single DNA chip. Puffenberger wore belted black Levi’s with a red shirt neatly tucked in, and he smelled of Old Spice. Puffenberger made very certain I understood everything he told me. To this end, he tended to rephrase his explanations, which I recorded on my Dictaphone, several ways. Then he made some notes on a sheet of paper, folded it, and handed it to me. Then he showed me a PowerPoint presentation, printed it out, and e-mailed it to me. To be sure, I was a willing recipient of all these explanations: The points made by geneticists can be hard to understand, and this was an important point. The point was, inbreeding does not cause genetic disease but it does increase the probability of its occurring—slightly.

  Puffenberger pointed out that Morton had grown up in the coalmining region of West Virginia, the national butt of inbreeding jokes. (In 2004 the governor of Virginia publicly protested the clothing retailer Abercrombie & Fitch’s marketing of a T-shirt that read, IT’S ALL RELATIVE IN WEST VIRGINIA.) Puffenberger himself grew up in Lancaster County. The Old Order Mennonite population he had used for his doctoral research was a geneticist’s dream, because it had stayed essentially isolated for roughly three hundred years, since two Anabaptist groups—the Old Order Mennonites and the Amish—had accepted William Penn’s invitation to immigrate to the United States. They lived on their farms and eschewed most of what civilization had to offer, such as television, cars (not all of them; some Mennonite groups now allow their members to drive, provided they paint their cars, including the normally chrome parts, black like the buggy, which has remained the privileged vehicle), and telephones—which meant that many of them married not just within their religious community but within the immediate vicinity, which is one of the ways they ended up with marriages between double first cousins.

  Contrary to all those West Virginia jokes, none of this meant that people had to be sick. If you do not carry the gene for any recessive disorder, marrying your double first cousin will probably not endanger your future children. But in a population where—as in most or all populations—some people carry some mutations for some diseases, those people’s cousins and other relatives are more likely than others to carry the same mutations.

  Take maple syrup disease, said Puffenberger. The carrier frequency among the Old Order Mennonites in Pennsylvania was roughly 10 percent—extremely high for any genetic disorder anywhere. The disease is found elsewhere—say, in Northern Europe, where the Mennonites originated—but the carrier frequency in the old country is roughly one in 300,000. The very small “source population”—the group that originally came over to the United States—must have included one or two people who carried the mutation, which reproduced efficiently over the following three centuries. “In that case the allele frequency in the population is about 5 percent,” he said—meaning that in all the genomes of all the Pennsylvania Mennonites, about 5 percent of the maple syrup genes would be abnormal: one abnormal gene per carrier, one carrier per ten people. “What inbreeding does, because inbreeding is the marriage of people who are closely related, you tend to share alleles, you tend to share more DNA than somebody who is not as closely related to you. What does that do? That increases the number of homozygotes at both ends of the distribution.” That is, genetic bad luck becomes unevenly distributed: Where in a population with little consanguineous marriage the 5 percent of “bad” alleles would be spread more or less randomly, in a population where relatives tend to marry, the bad genes will bunch up at one end of the spectrum while the vast majority remain homozygous for the healthy version of the gene. “The allele frequency is still 5 percent,” Puffenberger stressed. “But it means in the long run, in an isolated population with inbreeding, you can create more affected individuals, or, said in a different way, given a fixed incidence, you need a lower carrier frequency in that population to give you the same number of affected individuals. So as inbreeding increases in the population, you are going to increase the number of affected individuals. But the underlying problem is the high mutation frequency. One in ten is just too high. But it’s a random chance event that this mutation got in high frequency.”

  Puffenberger was on to his other topic of passionate debunking. He was a convinced opponent of the selective advantage theories of genetic disease. “You read a lot in medical literature about postulating that a mutation, for instance cystic fibrosis, got in a high frequency because of a carrier or heterozygote advantage,” he said. “But I find those explanations to be rather implausible at times. If there was a beneficial effect of being a carrier for maple syrup urine disease, why don’t we see carrier rates higher in other parts of the world? Is there something specific to Lancaster County that gives them a benefit to being a carrier for MSUD? Or is it just by chance, bad luck essentially?

  “I think you can make those arguments about any mutation, in any population. Particularly, if you think about something like cystic fibrosis, there is one mutation that’s in fairly high frequency—probably 75 percent of mutations in cystic fibrosis are one mutation—everyone who carries that mutation is related to one another, because that mutation happened one time on one chromosome a long, long time ago, about two thousand years ago. So how does that mutation rise in frequency? You might make the argument, if there is a selective advantage to being a carrier for cystic fibrosis, why aren’t other mutations equally high frequency? In fact, we know of hundreds of different mutations on that gene. All the rest of them have risen to fairly low levels. Why is that? Maybe propped up in a geographic isolate in Europe, a group of people who were isolated and had a high frequency of that, were then subsumed into a larger population and the mutation spread in that way. You can imagine that if the Mennonites suddenly decided to dissolve themselves and joined the general population, our carrier frequency of MSUD in Lancaster County would suddenly go up. So you can imagine that two thousand years ago they didn’t have a very big population running around Europe. There would be essentially lots of little populations, genetically distinct little populations, any one of which could have had a rise in some mutation, which then was spread as populations sort of merged together. And you can imagine, and you can make a plausible argument that mutations got to their high frequencies just by chance.

  “Just look at the surnames in a population. The distribution of surnames is going to be based on what? A random event: how many boys a family has. The most common Amish name in Lancaster County is Stoltzfus. One in four among the Amish in Lancaster County has the last name Stoltzfus. What’s the selective advantage there? Unless you argue that Stoltzfus men are inordinately attractive compared to other men, or had an inordinate amount of wealth and all the Amish women just want to marry Stoltzfus men, you’d have a hard time explaining why a single surname had risen to such a high frequency. It’s chance.
They had a lot of boys, probably in an early generation, probably had a bigger family. Maybe more of the boys stayed in the population.”

  The surnames made for a great analogy. I assured Puffenberger that I agreed with him, but that was not enough. “It’s a view that many people would agree with,” he granted me that much. “But then you see all these papers. There was a rather interesting article in Scientific American just a couple of months ago about founder mutations, and much of the article spent time talking about heterozygote advantage for all these mutations. We just don’t see that here.” Puffenberger had tested the theory several different ways. One was to look at areas of the genomes of Old Order Mennonites with an eye to areas of decreased diversity—parts of the genome where many different people would be similar to one another. Suppose being a carrier for maple syrup disease did not confer a selective advantage: That much seemed obvious, since the disease remained so rare in Europe. But perhaps there was a gene somewhere in the general maple syrup region that played some sort of important role, and among the Pennsylvania Mennonites, the maple syrup mutation just happened to tag along. Puffenberger was giving the selective advantage theory as much benefit of the doubt as he could muster, but it still did not work: Neither this part of the genome nor any other looked “selected for” in the Old Order Mennonites.

  He went further. He looked at a region of mitochondrial DNA in about 250 Mennonite and Amish individuals to see how much variety he could find there—specifically, to see if certain haplotypes were significantly more common than others. For the mitochondrial DNA, which is passed on through the maternal line, it worked roughly the same as with surnames, which are passed on patrilineally: “There are a couple of mitochondrial haplotypes that are very common in the population that were only introduced by a single woman two hundred years or two hundred and fifty years ago. And how did that get in such high frequencies? Was that mitochondrial DNA so superior that it is spread in the population by selection? You look at the genealogies, and your answer is right in the genealogy: They had a lot of girls. These events can be random. It’s all right to be random!”