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Allergy to dietary protein

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Author(s): Carlos Lifschitz

Journal: Pediatria Współczesna
ISSN 1507-5532

Volume: 8;
Issue: 3;
Start page: 145;
Date: 2006;
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Keywords: Allergy to dietary protein

ABSTRACT
Definition Although it has been suggested that the term of allergy be applied only to those with immediate allergic responses to food and with the presence of specific IgE antibodies, the term allergy is loosely applied to. Among the food allergies, we include the reactions mediated by IgE (hypersensitMty or immediate type allergy), as well as those produced by any other known immunologie mechanism (reactions not mediated by IgE). Incidence Food intolerance oceurs in approximately 5% of the pediatrie population. Incidence of up to 8% have been reported. Seventy five percent of infants will have symptoms in the first two months of life. A family history of atopic diseases is fo-und in 70% of patients. Pathogenesis Because the pathogenesis and symptoms of cow milk protein intolerance (CMPI; cow milk protein sensitive entero-pathy/cow milk allergy) and those of soy milk protein intolerance are similar, we will describe them as a single entity and refer to them as dietary protein intolerance (DPI). DPI may present in infants with or without a family history of atopy or in infants with or without previous manifestations of atopy. DPI can be preceded by an episode of acute enteritis or present suddenly without any overt predisposing conditions. It is postulated that the mechanism is an allergic one and a personal and family history of atopy is often present. The-re are morę than 20 protein fractions in cow milk and p-lak-toglobulin (not present in human milk) is the commonest cul-prit but a-lactoalbumin, casein, and bovine serum albuminę can also cause enteropathy. Symptoms Symptoms include: diarrhea, urticaria, eczema, rhinitis, ab-dominal pain, failure to thrive, vomiting, behavioral disturbances (erying spells, colic) and constipation. Gastrointestinal symptoms may mimie a prolonged gastroenteritis which may include vomiting, loose mucousy stools containing macro- or microscopic blood, and(or) failure to thrive. Hypoproteinemia may arise as a result of a protein-losing enteropathy. Secondary carbohydrate intolerance may oceur as a consequence of the blunting villi and depletion of the brush border disaccha-ridases. Whenever cow milk protein intolerance is suspected and a switch is madę to soy milk there is the possibility that an allergic reactions will recur. As many as 25% of children in-tolerant to cow milk react adversely to soy protein. Blood and mucus in the stools, with or without diarrhea characterizes protein-induced colitis. Proctoscopy or colono-scopywill reveal afriable mucosathat bleeds or a zone of hy-peremia around blood vessels. Biopsy may demonstrate changes of an acute colitis with erypt abscesses, depletion of mucus from rectal glands and inflammatory changes within the lamina propria. In food-sensitive colitis, eosinophilia is often found as well as the presence of IgE-bearing mononuc-lear biopsy materiał. Proctocolitis can also be observed in infants who are exclusively breast-fed. Smali intestinal enteropathies in infants associated to egg, fish, chicken and rice have been described. Another form of presentation of protein hypersensitMty is constipation. Diagnosis At present there is no widespread agreement concerning the criteria for diagnosing dietary protein. Despite the large number of publications describing different in vivo and in vi-tro tests to diagnose this entity, the response to challenge with the suspected offending protein remains the gold standard method to diagnose dietary protein intolerance. The procedurę on how to perform the challenge was described by Hill et al. Irwestigations Skin (prick) tests ('immediate') and the radioallergosor-bent test (RAST) produce false-positives as well as negatives but fail to identify problems not due to IgE, that is reactions that oceur after some hours. Although the positive predieti-ve value of a prick test is Iower than 50%, a negative skin test practically excludes the possibility that a patient will develop symptoms in a challenge test unless we are dealing with a re-action that is not mediated by IgE. If the smali intestine is affected, smali bowel biopsy will show a patchy enteropathy, with mostly a chronić, non-spe-cific inflammatory infiltrate which consists of lympho- and pla-smocytes and eosinophils, as well. The histopathology can re-semble celiac disease in relapse. Also the lamina propria may be infiltrated with eosinophils and(or) have an inerease in IgE plasma cells. The mucosa improves when the offending pro-tein(s) is removed from the diet. Laboratory tests are not generally necessary but findings may include: 1.Eosinophilia(>450'10/dl). 2.Positive skin tests to milk proteins. 3.Elevated total IgE. 4.Positive RAST to cow and(or) soy milk proteins (non- specific). 5.Low IgA and reduced C3. Differential diagnosis In patients with diarrhea, the following conditions need to be excluded: 1.Lactose malabsorption. 2.Celiac disease. 3.Giardiasis. 4.Irritable bowel syndrome (toddler's diarrhea). 5.Enteritis: infectious, autoimmune, inflammatory bowel disease, intractable diarrhea. 6.Intestinal lymphangiectasia. 7.Immunodeficiency syndrome. Treatment Dietary management of adverse reactions to foods In the exclusively breast-fed infant, intolerance is not to the mother's milk protein but to proteins from her diet elimi-nated in breast-milk. If elimination diet in the mother does not resolve the problem and the infant is clinically well and growing, it can be possible to explain the problem to the pa-rents and ignore the symptom. In the formula-fed infant, identifying the suspected allergen is the easiest of all situa-tions, and the problem can frequently be resolved with a change in the formuła. Almost every food consumed by man has been cited as an allergen in the literaturę. Many food dyes which have a low molecular weight and are not allergens in themselves act as haptens and become allergenic if linked to a larger protein molecule. Some substances may undergo transformation to allergens only after they have been through the digestive process. Cooking or food processing can also affect allerge-nicity: a hard boiled egg is less allergenic than a raw one. Cer-tain combinations of food may be allergenic while failing to give rise to symptoms when eaten separately. Allergy to one food is likely to produce cross-reactions with biologically re-lated compounds: if eggs are not tolerated then chicken sho-uld be suspected until proved otherwise; likewise beef and veal in milk protein allergy and broad beans, peas and lentils where peanuts are known to be allergenic. The allergenicity of some items may be dose related: one strawberry may be tolerated while a plateful will produce urticaria. It can be seen that the most common food allergens re-ported are milk, cheese and dairy products, egg, fish and shellfish, chocolate, citrus fruits, meat (particularly pork), nuts and wheat. Formuła alternatives Alternatives to cow milk fali into three broad categories: -soy milk-based feeds, rarely effective as a substitute for true casein hypersensitMty, -milkof another species, such as human, goat or sheep; the two latter are not recommended, and human only if the mother is capable or re-establishing lactation, -hydrolyzed protein from another source, which can be either animal, vegetable or synthetic. If feeding human milk is not possible, then milk protein hydrolysates or in some cases even aminoacid based formuła should be used.
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