The Many Forms of Allergic GI Disorders

Allergic GI Disorders
The incidence of food allergies is increasing. In infants, skin or gastrointestinal allergy may be a marker for allergic disorders later in life...

The incidence of allergy is increasing, particularly to food allergens. The occurrence of skin or gastrointestinal (GI) allergy in infants may be a marker for allergic disorders later in life, said John Kerner, MD, Professor of Pediatrics, Stanford University Medical School. His talk addressed the two basic types of adverse reactions to food.

The first type, food intolerance, is nonimmunologic and can be caused by an enzyme deficiency, a toxin, or a pharmacologic substance. The second type, food hypersensitivity (allergy), is an immunologic response to ingestion of food or an additive.

Foods that account for 90% of allergic reactions in children are cow's milk protein, eggs, peanut, soy, tree nuts, fish, and wheat. Food allergy can manifest as urticaria/angioedema, anaphylaxis, atopic dermatitis, respiratory symptoms, or a GI disorder.

When the infant's immature gut cannot adequately digest a food protein, the body may mount an immunologic response against it, usually by forming immunoglobulin E (IgE) antibodies. Alternatively, food antigens can cause a non–IgE-mediated reaction.

IgE-Mediated Disorders

Of these less common types of GI allergic manifestations, the most common are immediate GI hypersensitivity and oral allergy syndrome. The former typically involves nausea, abdominal pain, and emesis within 1 to 2 hours of exposure to the allergen, diarrhea within 2 to 6 hours, and often a history of atopy. Treatment is strict elimination of the implicated food allergen—which is generally milk, soy, egg, peanuts, shellfish, or wheat.

Oral allergy syndrome is characterized by immediate onset of burning and swelling of the lips, itching, and erythema, and a history of pollen sensitivity, particularly to ragweed or birch. These pollens cross-react with certain fresh fruit and vegetables, which the child should either avoid or eat only when cooked.

"Mixed" GI allergy syndromes, involving some IgE components and some non-IgE components, include allergic eosinophilic esophagitis and allergic eosinophilic gastritis/enterocolitis.

Non–IgE-Mediated Disorders

Non–IgE-mediated allergic GI disorders include dietary protein enteropathy, enterocolitis, and proctitis. The classic dietary protein enteropathy involves diarrhea, malabsorption, failure to thrive, vomiting, abdominal distension, and early satiety. Anemia, edema, hypoproteinemia, and protein-losing enteropathy are all characteristic. An x-ray reveals small bowel edema. Serum IgE is normal, and no peripheral eosinophils are evident. Onset is early and depends on exposure to the responsible antigen, usually cow's milk, soy, gluten, egg, or cod.

The pathology is marked by patchy subtotal villous injury, many intraepithelial lymphocytes, and few eosinophils. Strict elimination of the offending protein clears symptoms in 10 to 21 days. The condition resolves by 3 to 5 years of age.

Dietary protein enterocolitis can appear from birth to 1 year of age. It involves bloody diarrhea and anemia, emesis, abdominal distension, failure to thrive, protein-losing enteropathy, hypotension, and fecal polymorphonuclear neutrophil leukocytes. The primary responsible proteins are cow's milk, soy, ovalbumin, and casein and whey hydrolysates. Chronic inflammatory colitis with moderate enteropathy is characteristic. Stool exam reveals red blood cells, eosinophils, polymorphonuclear neutrophil leukocytes, and positive reducing substances. About 90% of patients respond within 3 to 5 days to hydrolyzed protein formula.

Dietary protein-induced proctitis is a common benign condition marked by blood-streaked soft to loose stools and sometimes constipation. Fecal leukocytes, mild peripheral eosinophilia, and hypoalbuminemia are characteristic. Age of onset is from 1 day after birth to 6 months of age. About 60% of infants with proctitis are exclusively breastfed; cow's milk, soy, and hydrolyzed protein also can cause the condition. Treatment with casein hydrolysate formula usually clears symptoms in 72 hours. The mother can resume breastfeeding but should first identify and eliminate the responsible antigen from her diet. The condition generally resolves by 9 months to a year.

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