BOSTON (AP) -- When 5-year-old Jenny Richardson orders fast food, it's french fries only or a hamburger without the bun. She doesn't share birthday cupcakes with her friends.

And now, because of Roman Catholic Church rules, she can't have part of her First Communion rite, either.

Jenny suffers from celiac disease, which causes her to get sick from eating gluten, a protein in wheat and other grains. She can safely eat rice.

The Archdiocese of Boston has told the family that the church cannot substitute a rice communion wafer for the traditional wheat one, citing 2,000 years of tradition and faith.

The Richardson family now worships at a Methodist church, where the rules on communion are more flexible because Methodists believe the bread and wine are symbolic, not the actual transubstantiated body and blood of Jesus.

"It was hard. It's hard to make a decision to change," says the girl's mother, Janice Richardson.

Though Jenny is two years away from the age when most U.S. Catholics make First Communion, the family started last fall to lay the groundwork.

Doug and Janice Richardson, who live with their three children in the Boston suburb of Natick, say they were told by their parish priest, the Rev. Dan Twomey, that Jenny could take communion in the form of wine instead of bread. They declined.

"She feels different wherever she goes but shouldn't be made to feel different in church," her mother says.

The family received a letter from Cardinal Bernard Law, who explained the church would not make an exception. Twomey this week referred questions about the matter to the archdiocese.

For people with celiac disease, gluten flattens the villi, the tiny fronds inside the walls of the small intestine that absorb nutrients. That makes celiac sufferers sick, lowers their resistance to other illnesses and causes fatigue.

The only treatment is a diet completely free of gluten. The Celiac Disease Foundation estimates as many as 1 in 250 people is affected by it.

Still, church experts say there are numerous reasons they cannot compromise on wheat.

"This is not an arbitrary sort of thing, and we're talking about a religious sacrament," says John B. Walsh, a spokesman for the Archdiocese of Boston. "Bread is central to the Eucharist because of the imagery of Scripture, because of the prayers of the Christian community going back thousands of years."

The Vatican takes the matter seriously enough that in 1994, it issued rules for all bishops to follow. Among them: "Special hosts [which do not contain gluten] are invalid matter for the celebration of the Eucharist."

"I think part of the problem is we are so accustomed to all these little round, pre-cut hosts we've lost any real sense we're taking part in one loaf," says the Rev. Austin Fleming, pastor of Our Lady of Christian Help Church in Concord, Mass. "We many are sharing one bread and becoming one with Christ. We can't make different flavors for different folks and maintain that theological reality."

Massachusetts Lt. Gov. Jane Swift is a practicing Catholic and has celiac disease. She said this week she plans to send a note to Jenny to tell her "just that I share the same disease and that she'll be able to all the things she wants do to in her life." Swift would not discuss how she handles the disease in church.

Annette Bentley, president of the American Celiac Society and a practicing Catholic, says some priests quietly make a substitution to help parishioners. "To be Christian is to be more flexible," she says.

Jenny's mother says even if the church were to come around now, the family's decision to leave is permanent.

"I believe Jesus would have made an exception," she says.