Drug helps PKU patients with diet


Published: Thursday, January 17, 2008 at 6:01 a.m.
Last Modified: Wednesday, January 16, 2008 at 11:58 p.m.

For a baby born with the rare genetic disorder phenylketonuria, or PKU, it is a life sentence.

Facts

About PKU, or phenylketonuria

Rare genetic disorder caused by a deficiency of the enzyme phenylalanine hydroxylase.

Elevated levels of phenylalanine will affect brain growth.

Estimated to occur in 1 in 10,000 Caucasian births, or 1 in 20,000 Asian infants.

Has been screened for at birth for decades.

No cure; those who have it are on a strict diet for life.

Those with PKU can't break down one specific amino acid, phenylalanine, that's found in meat, milk, eggs and other foods.

There is no cure, so PKU patients are effectively on a "diet for life."

Most kids with PKU have never enjoyed a slice of pizza, a peanut butter and jelly sandwich or an ice cream cone. They must stick to a strict diet that limits the amount of phenylalanine they consume in foods. If not, the amino acid can accumulate in the blood, eventually reaching levels that are toxic to the brain.

Complications can include mental retardation, mental illness, seizures and other neurological problems.

PKU is one of a number of disorders that babies are screened for at birth. It occurs in about one in 10,000 Caucasian infants, one in 20,000 Asian births and less frequently among African-Americans.

"It is a condition that will affect a person for their whole life. They will not grow out of it, but with proper management, it shouldn't shorten their life-span," said Dr. Bryce Heese, who is an assistant professor of pediatric genetics and metabolism in the University of Florida College of Medicine.

A new drug from California-based BioMarin Pharmaceutical called Kuvan recently received approval from the Food and Drug Administration. It offers some PKU patients a little more dietary leeway, according to Heese.

It doesn't work for everyone, he emphasized, but in those it does work for, Kuvan significantly reduced the phenylalanine levels, which allowed them better control of their diet.

"That's particularly important in adolescents, who want to think - and eat - for themselves," he added.

The standard treatment for PKU is still strict dietary management with supplements so that the patient isn't missing out on other nutritional elements. Heese said there is another approach of giving large amino acid supplements to try to block absorption of phenylalanine.

"There are researchers working on gene therapy, although we're not there yet. That would allow you to correct the defect on the genetic level," he explained.

"None of these approaches are there yet, so right now it is a matter of management," he said. "And for select individuals, there is now Kuvan."

Heese said PKU was among the first disorders to be extensively screened for in newborns, and hence is one physicians know the most about. Dozens of other disorders have followed, and have proven to be treatable and manageable, if they are recognized early.

"It is important to find these kids early, in order to optimize their development and quality of life in the future," he said.

Physicians at Shands at UF probably see more than their share of PKU patients, according to Heese, because any parent of a PKU child will seek out specialists to help them deal with the disorder and its restrictive diet.

Kuvan, which is offered at Shands, doesn't reduce phenylalanine levels for everyone, he emphasized, but in the cases where it works, "patients benefit by removing some of the restrictions on their life."

Diane Chun can be reached at 352-374-5041 or chund@gvillesun.com

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