The trouble for Daniel Tully, then 12 and an excellent student and athlete in Brooklyn, began 20 months ago, when he developed what seemed like a virus that kept recurring, each time sending him to bed and keeping him from school for a week.

In January, he came down with an intestinal bug from which he never seemed to recover. He developed severe headaches whenever he tried to read or concentrate, became extremely weak, mentally foggy and unable to go to school at all. He vomited violently after meals, lost weight, and eventually could not walk unaided.

“I had to carry him to the bathroom,” recalled his father, Ed Tully.

When a child develops such a devastating constellation of symptoms, you’d think his doctors might consider testing for celiac disease, an autoimmune reaction to dietary gluten that can destroy the small intestine. Awareness of the problem has never been greater.

But even in the most sophisticated medical settings, the diagnosis can be missed or the tests done incorrectly. Over four days in a local hospital, Daniel’s doctors performed an intestinal biopsy. But only two samples were taken, which missed the severe damage in his small intestine.

He finally saw a pediatric immunologist and was given the blood test specific for celiac disease. It was unequivocally positive. The diagnosis was confirmed by a second intestinal biopsy, this time with the recommended six or more samples.

Daniel began a strict gluten-free diet five months ago and is gradually recovering. With intensive physical therapy and a diet rich in meat, he is regaining lost strength, weight and stamina. His doctors say it may take a year, but he eventually will achieve normal growth — as long as he sticks religiously to the diet.

Gluten is a protein in grains like wheat, rye and barley that contains gliadin peptides. In people with celiac disease, these can trigger an autoimmune reaction that damages the villi, tiny projections lining the small intestine that absorb nutrients from food into the body. Like Daniel, people with celiac disease must avoid wheat, rye or barley, or any of the thousands of products or ingredients made from these grains. Some must also abstain from oats.

The disease runs in families: Some of Daniel’s first and second cousins have it, and Daniel’s younger sister is now being tested for it.

First-degree relatives of someone with celiac disease should also be tested for it, even if they have no symptoms. If another person in the immediate family has the disease, second-degree relatives should be tested, Dr. Joseph A. Murray, a gastroenterologist at the Mayo Clinic, said in an interview.

“Celiac disease is now five times more common than it was 50 years ago, and that’s not just the result of better diagnoses,” said Dr. Murray, who is also editor of “Mayo Clinic Going Gluten Free,” to be published in November. “We looked at old stored blood samples, and that showed a real increase in incidence.”

For reasons unknown, celiac disease now affects one in 100 Caucasians, Dr. Murray said. It does occur in other racial groups, but is believed to be much less common.

Hygienic extremes may be to blame for the increase: Overzealous cleanliness has been linked to a rise in autoimmune diseases. But experts speculate the increase also may have to do with how grains are bred these days, or the overreliance on formula to feed infants. Although traditionally considered a disease that shows up in childhood, people of all ages may develop it. One person I know was diagnosed in his 50s, another in her 60s.

But the overwhelming majority of people with celiac disease remain undiagnosed. The most recent data show that only 17 percent of Americans with the disease know they have it. Those who are not avoiding gluten risk developing a host of debilitating, sometimes fatal complications, including cancer.

A main reason for this lag in detection is the long and confusing list of signs and symptoms, some of which may be mild enough to be easily ignored or attributed to another condition, like irritable bowel syndrome or an allergy.

Abdominal pain and bloating are the most common signs. But according to a recent review in JAMA Pediatrics, possible symptoms include chronic or intermittent constipation; vomiting; loss of appetite; weight loss (or, in children, growth failure); fatigue; iron deficiency anemia; abnormal dental enamel; mouth ulcers; arthritis and joint pain; bone loss and fractures; short stature; delayed puberty; unexplained infertility and miscarriage; recurring headaches; loss of feeling in hands and feet; poor coordination and unsteadiness; seizures; depression; hallucinations, anxiety and panic attacks. “Doctors have to raise their index of suspicion,” Dr. Murray said. “At least half of patients don’t have diarrhea. It can present in so many ways.”

About one-third of his patients had asked doctors on their own for testing, he added. It is critically important to be tested before going on a gluten-free diet, which can disguise the intestinal damage characteristic of the condition. Those already eating a restricted diet would have to return to gluten (say, eating two slices of bread a day for two weeks) for the test to be accurate.

Avoiding gluten has become easier in recent years as companies have loaded store shelves with gluten-free foods. A new Food and Drug Administration rule stipulates that any food labeled gluten-free must contain less than 20 parts per million of gluten (the amount in 18 slices of gluten-free bread), considered harmless for most celiac patients.

All uncoated, unprocessed meats, poultry, fish, beans, nuts, vegetables and fruits are naturally gluten-free, and can be labeled as such. But to be safe, consumers must read labels diligently to spot hidden hazards, like hydrolyzed vegetable protein, and learn to ask detailed questions about how food is prepared when dining out. Even reusing water in which wheat pasta is cooked can be hazardous.

This article was originally posted on The New York Times website by Jane E. Brody, and can be found here.

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