Q. I've been having a lot of gas recently. In addition, I've been getting sores in my mouth. Any ideas about what's causing this?

A. I receive many questions from readers looking for help in diagnosing their health problems. I'm extremely careful to avoid giving personal medical advice. I'm a journalist who provides general information about health. Only a doctor who has examined a patient is qualified to diagnose, and even the experts have trouble figuring out what's wrong with patients.Here's an example of a problem that exemplifies the difficulty of diagnosis. The following are symptoms of a common disease you may never have heard of. Some of the symptoms contradict each other. Here goes:Gas, abdominal pain, chronic diarrhea, constipation, pale stool, weight loss, weight gain, fatigue, unexplained anemia, bone or joint pain, osteoporosis, behavioral changes, tingling numbness in the legs, muscle cramps, seizures, missed menstrual periods, infertility, recurrent miscarriage, delayed growth, mouth sores, tooth discoloration and itchy skin rash.These are symptoms of celiac disease, a digestive ailment that damages the small intestine and interferes with nutrition. People with celiac disease cannot tolerate a protein called gluten, which is in wheat, rye and barley.If you notice or experience any of the signs or symptoms common to celiac disease, see your doctor.Celiac disease is commonly underdiagnosed because some of its symptoms are similar to those of other diseases. Celiac disease often is confused with irritable bowel syndrome, iron-deficiency anemia, Crohn's disease, diverticulitis, intestinal infections and chronic fatigue syndrome.There are other reasons for the underdiagnosis of celiac disease. Many doctors and health care professionals are not knowledgeable about the disease. And only a small number of U.S. laboratories are experienced and skilled in testing for celiac disease.It's estimated that about 1 in 100 people in the world has celiac disease. However, Americans are not routinely screened for celiac disease. More research is required to determine an accurate number of the people with celiac disease in the U.S.Celiac disease runs in families. Sometimes celiac begins after surgery, pregnancy, childbirth, viral infection or severe emotional stress. Some people develop symptoms as children, others as adults. Although celiac disease can affect anyone, it tends to be more common in people of European descentA person with celiac disease may have no symptoms. People without symptoms are still at risk. The longer a person is not treated for the disease, the greater the chance of developing malnutrition and other complications such as loss of calcium and bone density, intolerance to dairy products, cancer and disorders of the nervous system.The only treatment for celiac disease is to follow a gluten-free diet. For most people, following this diet will stop symptoms, heal existing intestinal damage and prevent further damage.The obvious foods with gluten are breads, pastas and cereals. But gluten is also in many processed foods such as frozen French-fried potatoes and soy sauce. Many products such as cosmetics, household cleansers, stamp and envelope adhesive, medicines and vitamins contain gluten.There are gluten-free substitutes for many problematic foods. Many cities have specialty grocery stores that sell these gluten-free substitutes.The Times News Inc. and affiliates (Times News) do not endorse or recommend any medical products, processes, or services or provide medical advice. The views of the author do not necessarily state or reflect those of the Times News. The article content is not intended as a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician, or other qualified health provider with any questions you may have regarding a medical condition.