When Joni Arneson goes out to eat, she's not likely to order a steak. For one thing, she doesn't like meat. But more importantly, an overload of protein could give her a severe headache.

Arneson is a 27-year-old mother of two living with phenylketonuria, or PKU, which is a metabolic disorder that involves a malfunctioning or missing enzyme that doesn't allow a person to process an amino acid called phenylalanine, or phe. The body uses phe to make proteins.

Most of us only learn about PKU if we have a newborn baby. Â A nurse comes in, pricks the baby's tiny heal and smears a blood sample on a piece of filter paper. PKU is one of 29 conditions that babies are now screened for.

If phe levels go unchecked and uncontrolled in an infant or toddler with  PKU, severe mental retardation can result.

Chances are the baby's PKU screen will be negative, but Arneson was the one in the one in 10,000, babies that are born with PKU.

"It's tough," she said from her home in Joplin, a community of a few hundred residents about halfway between Shelby and Havre. "When you go out to restaurants, people look at you funny. You order just fries, or a salad and fries and people look."

Arneson doesn't eat out often. She sticks to a low-protein diet. She eats a lot of potatoes.

"Usually for breakfast, I have hash browns and toast," she said. "At lunch, I have soup. For dinner, we usually have a potato and chicken - we eat a lot of chicken stir fry."

Her options have expanded recently, however. A little more than a year ago, she started taking a drug called Kuvan, which helps her body process phenylalanine.

"On Kuvan, I can eat meat," she said. "I don't like it, but when you haven't had it all your life - you have to get used to eating it I guess."

What she has gotten used to, a little too used to, is pizza and nachos. But Arneson checks her phenylalanine levels, or phe, monthly. She takes her own blood sample and sends it to the state lab for testing.

PKU tests were administered for the first time in 1963. And as Arneson proves, when the disorder is identified early enough, PKU patients can live somewhat normal lives.

Although she is past the danger of developing brain damage, she still must monitor her diet.

Nutritionists and genetic counselors at Shodair Children's Hospital in Helena work with patients who have metabolic disorders like PKU. Shodair, in fact, contracts with the Department of Public Health and Human Services to carry out the genetic testing on newborns.

Joan Reichert, a nutritionist at Shodair, says she works with about three PKU patients each week - from parents of newly diagnosed infants to adults.

"It gets easier as the patient gets older," Reichert said.

Parents must measure out everything for an infant's diet, use special formula and make sure phe levels are checked weekly.

But as a PKU patient gets older, drugs like Kuvan can be used in conjunction with a low-protein diet. Pharmaceutical companies and some food companies make products that are PKU friendly like low-protein pastas and breads and also special muffin and cookie mixes.

The items can be costly and are not available at regular grocery stores, but Reichert said that these medical foods are covered by insurance in Montana and can easily be ordered.

If phe levels become too high in a PKU patient, Reichert said they can often feel it.

"I get headaches and my concentration isn't good," Arneson said.

Too low phe levels can also be a concern.

Another consideration for an adult with PKU is, of course, the possibility that his or her kids could have PKU. According to Shodair genetic counselor Tessa Pitman, the chances of Arneson's children having PKU depended on whether or not her husband is a carrier of PKU.

Pitman said that approximately one in 50 Caucasians is a PKU carrier and the disorder happens more often in people whose families come from Ireland and other parts of northern Europe as well as Turkey. Native Americans are another group with a higher incidence of PKU.

If Arneson's husband is a PKU carrier, the couple's chance of having a child with PKU is 50 percent, Pitman said. If Arneson's husband is not a carrier, the chance of them having a child with PKU decreases to 1 percent.

"PKU is inherited in an autosomal recessive manner affecting both girls and boys equally," Pitman said. "Everyone has a pair of genes that make the PAH (phenylalanine hydroxylase) enzyme. In children with PKU, neither of these genes works correctly. These children inherited one non-working gene for the condition from each parent. Parents of children with PKU do not have the condition themselves. Instead, each parent has a single non-working gene for PKU. They are called carriers. Carriers do not have PKU because the other gene of this pair is working. When both parents are carriers, there is a 25 percent chance in each pregnancy for the child to have PKU.  There is a 75 percent chance the child will not have PKU. The risk of a sibling of a child with PKU is a carrier is two-thirds." Â

Although people can be tested for PKU carrier status, most people don't opt to have it done since PKU is a manageable condition," Pitman said.

Arneson's 6 and 2-year-old children are healthy and do not have PKU.

"They are a miracle," Arneson said.

Montana Metabolic Day

Shodair Children's Hospital is hosting a Montana Metabolic Day event on Saturday at Carroll College. Shodair community relations director Anastasia Burton says approximately 50 people from around the state have registered.

Montana Metabolic Day will include presentations by experts in metabolic conditions, a cooking demonstration on foods that are appropriate for PKU patients and fun activities for children with metabolic conditions.

Peggy O'Neill: 447-4074; peggy.oneill@helenair.

com.