Allergy to cooked white potatoes in infants and young children: A cause of severe, chronic allergic disease

Allergy to cooked white potatoes in infants and young children: A cause of severe, chronic allergic disease Liliane F. A. De Swert, MD, a Pascal Cadot, PhD, b and Jan L. Ceuppens, MD, PhD b,c Leuven, Belgium Background: Cases of allergy to cooked potato in children have been reported, some with immediate and others with late reactions. The clinical effects of chronic allergic reactions to potato and the effectiveness of diet on such reactions have not been described previously. Objective: We sought to evaluate the importance of cooked potato as an allergenic food in individual cases of atopy in children. Methods: Eight atopic children were selected on the basis of suspicion of allergy to cooked potatoes: all had potato-specific IgE, 2 of 8 had experienced immediate allergic reactions, and 6 of 8 had eczema that improved with a potato-elimination diet (decrease in severity scoring of atopic dermatis [SCORAD] index of >50%). The patients were evaluated by using skin prick tests with homemade cooked and noncooked potato extracts and with a commercial extract and by using IgE immunoblots from SDS-PAGE patterns of potato extract. Seven patients were challenged with cooked potato. The control group consisted of 9 age-matched atopic children, 8 of them with eczema. Results: The mean SCORAD index decreased from 43.3 before to 11.5 after elimination of potato from the diet. Potato CAP values ranged from 3.71 to greater than 100 kua/l. Potato challenge results were positive in 7 of 7 patients. Skin prick test responses were positive for cooked potato extracts in 7 of 7 patients, for noncooked extracts in 7 of 7 patients, and for the commercial extract in 8 of 8 patients compared with in 0 of 9, 1 of 9, and 1 of 9 subjects in the control group, respectively. During immunoblotting, 8 of 8 patient sera recognized one or more protein bands compared with 0 of 9 control subject sera. Conclusion: Allergy to cooked potatoes is a cause of severe allergic disease, with immediate eczema in some atopic infants and young children. (J Allergy Clin Immunol 2002;110:524-9.) Key words: Cooked potato, allergy, children, atopic dermatitis Food allergy is the main cause of allergic symptoms in infants and young children. 1 A limited number of foods are responsible for the majority of food-induced allergic reactions in children, namely cow s milk, egg, peanut, soy, fish, and wheat. 1-3 From a Pediatric Allergy, the Department of Pediatrics, b the Laboratory of Experimental Immunology, and c the Division of Allergy and Clinical Immunology, University Hospital Gasthuisberg, Leuven. Supported in part by a grant from Levenslijn Allergie (FWO grant 7-0013-00). Received for publication April 5, 2002; revised June 6, 2002; accepted for publication June 11, 2002. Reprint requests: Liliane De Swert, MD, Department of Pediatrics, University Hospital Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium. 2002 Mosby, Inc. All rights reserved. 0091-6749/2002 $35.00 + 0 1/87/127435 doi:10.1067/mai.2002.127435 524 Abbreviations used PBS-NFDM: PBS containing 0.2% defatted dried milk SPT: Skin prick test White potato (Solanum tuberosum) is a very common ingredient in the diet of Western countries, and in its cooked form it is one of the first solid foods introduced in the child s diet, usually around the age of 4 to 6 months. Potato allergy in children has been reported in few cases only. 4-10 In adults allergy to raw potato is mainly known as a manifestation of oral allergy syndrome in patients with pollen allergy, especially in housewives, who experience itching, rhinoconjunctivitis, and, in some cases, asthma during the peeling of potatoes. 11-14 These cases of hypersensitivity to raw potato seem to be caused by IgE crossreacting with pollen of birch, 13 grass, or mugwort. 15,16 Other authors also described contact dermatitis in food handlers and housewives, with immediate, as well as late, reactions to raw potatoes. 17 In children allergy to raw potatoes with immediate onset of symptoms has been described by 3 groups. 4-6 Wahl et al 7 investigated sera of 12 children with immediate hypersensitivity reactions to potatoes using RAST, immunoblotting, and histamine release. 7 Cases of allergy to cooked potatoes have been reported in children only 8-10 with both immediate 8,9 and late reactions. 9,10 However, except for the case described by Castells et al, 8 the severity of the symptoms caused by allergy to cooked potato has not been described. Thus far, skin prick tests (SPTs) have been performed with noncooked potato extract only. In a preliminary study we reported the elicitation of immediate and late symptoms by cooked potatoes in young atopic children. 9 Recently, Majamaa et al 10 showed that cooked potato can be an allergenic food in a selected group of infants with atopic dermatitis. The presence of IgE antibodies directed against several potato allergens with molecular masses of 14 to 65 kd was demonstrated in the patient studied by Castells et al 8 and in 3 patients described by Wahl et al. 7 Seppälä et al 18,19 identified patatin and 4 other potato proteins as IgE-binding proteins for children suspected of having potato allergy and a positive SPT response to raw potato. In this study we show, by means of evaluation of symptoms before and after elimination of potato from the diet and provocation, that hypersensitivity to cooked

J ALLERGY CLIN IMMUNOL VOLUME 110, NUMBER 3 De Swert, Cadot, and Ceuppens 525 TABLE I. Primary symptoms, potato CAP, and provocation with cooked potato Age (mo) at: Provocation with cooked potato Elimination Provocation CAP potato* Dose Time No. of Patient Primary symptoms of potato with potato (kua/l) ingested (g) lapse challenges Symptoms 1 Eg, Rh, Wh 25 55 9.12 120 (days 1-3) 5 h 2 I, E 24 h C, Wh 2 Eg, V 15 28 24.6 15 (day 1) 30 min 2 V 3 E,A, U 6 49 7.2 5 (day 1) 15 min 2 U, A 4 Eg 8 ND 55.2 ND ND ND ND 5 E 9 17 34.7 120 (days 1-3) 48 h 2 E 6 E, V 10 12 49.7 35 (day 1) 45 min 1 U, V 7 Eg 14 20 >100 15 (day 1) 30 min 1 I, R 120 (days 1 and 2) 24 h E 8 U,A, Wh 3.5 7 1.09 50 (day 1) 1 h 1 U, V, Wh, R Eg, Generalized eczema; Rh, rhinitis; Wh, wheezing; I, itching; E, eczema; C, coughing; V, vomiting; A, angioedema; U, urticaria; R, rash. *CAP potato value before elimination of potato from the diet. Potato dose ingested on the first challenge day and repeated during the following days. Time lapse in minutes or hours between onset of challenge and onset of symptoms. potatoes was responsible for severe symptoms of atopic disease in 8 young children. Results of skin tests with cooked and noncooked potato extracts, of total and specific IgE measurements, and of SDS-PAGE immunoblots with potato are compared with the results of other studies on the subject. METHODS Ethics The ethical committee of the University Hospital Gasthuisberg, Leuven, Belgium, authorized this study, and all parents gave informed consent to participate in the study. Patients At the pediatric department s outpatient clinic for allergy, we selected 8 children who were suspected of having allergy to cooked potatoes. Criteria for selection were (1) to have shown immediate allergic symptoms after ingestion of cooked potatoes, to have shown a decrease of at least 50% in the severity of eczema after the sole withdrawal of potato from the diet, or both, and (2) to have a positive CAP result for potato. At enrollment in the study, the patients, all boys, were aged 3.5 to 25 months (median, 11.3 months; Table I). Six patients had eczema since the age of 3 to 5 months (generalized eczema in 4 patients), for which they all received adequate topical treatment with emollients and corticosteroids. Of these patients, 4 had positive SPT responses and specific IgE levels for cow s milk and egg white, whereas the other 2 patients had positive SPT responses and IgE levels for egg white only. All 6 patients had been treated with a cow s milk and egg-free diet, without substantial improvement. In addition to their eczema, 2 of the children presented with vomiting after solid meals and one with wheezing and rhinitis. Two other patients had immediate symptoms after eating cooked potato. Of them, one boy with cow s milk and egg allergy and eczema had urticaria and angioedema at the age of 6 months after eating potato. The other patient, without sensitization to cow s milk and egg, had urticaria, angioedema, and wheezing after a meal containing cooked potatoes at 3 subsequent occasions at the age of 3.5 months. Both patients had been put on a potato-elimination diet. On enrollment, the patients were skin tested with a commercial extract of potato. Potato-specific IgE levels were determined, as were total IgE levels. For the 2 patients who were already on a potato-elimination diet, this was continued. The 6 patients still receiving potato until enrollment were also put on a potato-elimination diet. Other treatments and dietary restrictions were kept unchanged. The patients were then reevaluated for their symptoms after a period of 4 to 12 weeks. At the age of 7 to 55 months (median, 26 months), while still on a potato-free diet, the patients were skin prick tested with homemade potato extracts and with the commercial potato extract. Total IgE levels and potato-specific IgE levels were determined. In addition, a challenge test with cooked potato was carried out. Control subjects The control group consisted of 9 children, 5 boys and 4 girls aged 18 to 50 months (median, 25 months), with IgE-mediated cow s milk allergy. Their parents consented to skin prick testing. Eight children had eczema; of them, one boy also had a history of gastrointestinal symptoms, and one girl had been wheezing and had experienced episodes of urticaria and angioedema. One child had a history of gastrointestinal symptoms only. All children became symptom free on a cow s milk and egg-free diet. They all consumed potatoes regularly. Scoring of the severity of atopic dermatitis The severity of atopic dermatitis was scored according to the SCORAD method accepted by the European Task Force on Atopic Dermatitis. 20 The extent of the lesions was evaluated by score A, their intensity by score B, and subjective complaints by score C. Challenge with cooked potato The patients were on a potato-free diet for at least 2 months at the time of the challenge. They were in a fasting state, and if they were receiving medication, it was withheld on the morning of the challenge. For those patients suspected of having immediate reactions after ingestion of potato, intravenous access was established. The challenge was carried out with potato of the same type as consumed regularly before. It was cooked the morning of the challenge. The challenge procedure was open, starting with the application of a small amount of cooked potato at the inner side of the lower lip. If no reaction occurred after 15 minutes, we continued with doses of 5, 10, 20, 40, and 45 g of potato, respectively, given at 15- minute intervals until appearance of characteristic symptoms or until reaching the total dose of 120 g of cooked potato. This is the equivalent of 2 medium-size potatoes. During the whole challenge period, a trained nurse observed the children, and an experienced physician registered symptoms of allergic reactions, if any were present.

526 De Swert, Cadot, and Ceuppens J ALLERGY CLIN IMMUNOL SEPTEMBER 2002 25 mmol/l TRIS, 192 mmol/l glycine, and 20% methanol. The membrane was next blocked in PBS containing 0.2% defatted dried milk (PBS-NFDM 0.2%) before overnight incubation at 4 C in patient serum (125 µl) diluted in 0.1% PBS-NFDM. After washing, bound IgE was detected with mouse anti-human IgE mabs (CLB), followed by peroxidase-conjugated rat anti-mouse kappa light-chain antibodies (Biosource Europe). Dilutions and washes were made with 0.1% PBS- NFDM. Bands were revealed by means of incubation in TMB (KPL). Total IgE levels and potato CAP values Total serum IgE (Pharmacia) and potato-specific IgE levels determined by means of CAP (Pharmacia) were measured before withdrawal of potato and at the time of provocation and skin testing. CAP values of greater than 0.35 kua/l were considered positive. FIG 1. SCORAD index in 6 patients with severe eczema before and after a 4- to 12-week period of elimination of potato from the diet (P =.0312, Wilcoxon signed-rank test). The children were kept under controlled conditions for 2 hours after the challenge. If no symptoms appeared within that time, the parents were asked to give the child the same amount of cooked potatoes as used previously on the following days (at least 2 medium-size potatoes a day), while keeping the further diet unchanged. The patients were reevaluated after 2 days or earlier if there was any reaction. Reactions were noted, and a physical examination was performed. Reactions occurring within minutes up to 2 hours after challenge were considered immediate reactions, and reactions with later onset were considered late-phase reactions. 21,22 We planned to perform 2 challenges within 1 month, with an interval of at least 1 week, for those patients who would show only a late reaction. 21 For children with immediate gastrointestinal symptoms, such as nausea and vomiting, a second challenge was carried out. 23 Urticarial lesions consisting of a few small perioral wheals only were not considered a positive response. 24 Potato extract Potato extracts of 2 cultivars, Bintje and Charlotte, were prepared essentially according to the method of Rudeschko et al. 25 Briefly, pieces of potato bulb were put in diacetone alcohol (50 g/100 ml) for 10 minutes at 20 C, before 150 ml of precooled acetone was added. The mixture was kept overnight at 20 C. The precipitate was rinsed at 4 C twice with acetone and once with acetone/ether (1:1) and then left to dry. The resulting powder was then dissolved in distilled water for 1 hour at 4 C while stirring. After centrifugation for 45 minutes at 12,000g, the supernatant was divided into 2 parts. The first part was filtered through a 0.45-µm membrane, placed in aliquots, and kept at 20 C until use. This part was referred to as the noncooked potato extract. The second part of the extract was boiled for 5 minutes and then cooled at room temperature before filtration through a filter paper (Whatman no. 1) and a 0.45-µm membrane. Aliquots were stored at 20 C until use. This part was referred to as the cooked potato extract. For skin prick testing, both cooked and noncooked extracts were prepared in 50% glycerol (final concentration) with protein concentrations of 500 and 50 µg/ml, as measured with a Coomassie blue assay (Bio-Rad). Immunoblotting and electrophoresis SDS-PAGE was carried out in 13% polyacrylamide gels with 5% stacking gels, according to the method of Laemmli, 26 under reducing conditions. An amount of 30 µg (Bintje) of protein per centimeter was loaded. After the run, separated proteins were transferred at 100 V for 3 hours onto a polyvinylidene difluoride membrane (Immobilon-P, Millipore) by means of electroblotting in transfer buffer composed of Skin prick tests SPTs were performed with a commercial potato extract (HAL) and with homemade cooked and noncooked potato extracts of Bintje and Charlotte cultivars. SPTs were performed with a microlance (Becton Dickinson) and read after 15 minutes. Maximal and orthogonal diameters of the wheal reaction were recorded, and the mean diameter was calculated. One milligram per milliliter of histamine diphosphate (HAL) was used as a positive control, and Coca solution in 50% glycerol was used as a negative control. An SPT response was considered positive when the mean wheal diameter was 3 mm greater than that produced by the negative control. Statistics Results were analyzed with the Fisher exact test and the Wilcoxon test. RESULTS Clinical data The severity of atopic dermatitis before and after elimination of potato from the diet was scored in 6 patients. The mean SCORAD index decreased from 43.3 before to 11.5 after elimination of potato (Fig 1). In each patient the decrease in severity of eczema was the result of a reduction of at least 50% of all 3 individual scores (ie, extent, intensity, and subjective complaints, respectively). The mean score for extent of eczema decreased from 43.6 to 11.6, that for intensity decreased from 6.5 to 1.7, and that for subjective complaints decreased from 7.7 to 2.4. Interestingly, the boy who had been coughing and wheezing continuously was free of those symptoms after withdrawal of potato concomitantly with the improvement of his eczema. Vomiting subsided in the 2 patients who had been vomiting. Potato provocation test After an elimination period of 2 to 43 months (median, 15 months), 7 patients underwent a provocation with cooked potato (Table I). Patient 4 was not challenged because the parents refused. Challenge results were positive in all 7 patients tested. Five patients had an immediate reaction, which was followed by a late reaction in one of the patients. Two children had a late reaction only, with extensive erythematosquamous lesions over the trunk, arms, and legs and severe itching. One of those children also had cough, dyspnea, and wheeze after 2 challenges. All symptoms subsided within a few days.

J ALLERGY CLIN IMMUNOL VOLUME 110, NUMBER 3 De Swert, Cadot, and Ceuppens 527 Immunoblotting In the SDS-PAGE immunoblots of noncooked potato extract, 8 of 8 patient sera recognized one or more protein bands (Fig 2). Seven sera recognized a double protein band of about 40 kd. Serum H recognized this band only. Five sera recognized a protein band in the range of 17 to 18 kd, and for serum A, this was the only protein band that was recognized. Protein bands of approximately 14, 16, 20, 23, and 25 kd were recognized each by 2 different sera. Serum B also recognized a protein band of approximately 60 kd, and serum G also recognized protein bands of approximately 27, 38, and 85 kd, respectively. In the control group IgE immunoblots from SDS- PAGE patterns of potato extract were negative in 8 of 8 sera (data not shown). Total serum IgE levels and potato CAP values Potato CAP values were determined in all patients before withdrawal of potato and in 7 of 7 patients at the time of provocation. Results ranged from 1.09 to greater than 100 kua/l (Table I) and from 3.71 to greater than 100 kua/l, respectively. In the control group potato CAP results were negative in 5 of 6 children, whereas the result was 0.49 kua/l in one girl. Total IgE levels were determined in all patients before withdrawal of potato and in 6 of 7 patients at the time of provocation and ranged from 11 to 11,509 KU/L (mean, 2359 KU/L) and 377 to 2385 KU/L (mean, 1270 KU/L), respectively. Skin prick tests SPTs with homemade cooked and noncooked potato extracts were performed in 7 of 8 patients (Table II). All had a positive SPT response to one of the cooked potato extracts; 2 of 8 patients already had positive responses to a concentration of 50 µg/ml. The same 7 patients also had a positive SPT response for both noncooked potato extracts. SPT responses with the commercial extract were positive in all patients (Table II). Patient 8, who had a negative SPT response to the commercial extract at the time of enrollment, had a positive response to it at the time of provocation. In the control group all the children were tested with concentrations of 50 and 500 µg/ml of the cooked potato extracts, and all had negative responses (Table II). Of the 8 control subjects tested with the noncooked potato extracts, one girl had a positive SPT response for the highest concentration of Bintje cultivar. That same child was the only one of the 9 control subjects with a positive SPT response to the commercial extract. DISCUSSION This is the first study to show, by means of evaluation of symptoms before and after elimination of potato from the diet, that allergy to cooked potato might be responsible for severe, chronic allergic disease, especially eczema, in young children. FIG 2. IgE immunoblots from SDS-PAGE gel showing the reactivity to Bintje proteins of patients 1 (lane A), 2 (lane B), 3 (lane C), 4 (lane D), 5 (lane E), 6 (lane F), 7 (lane G), and 8 (lane H). Molecular masses are indicated on the left (in kilodaltons). Allergy to cooked potato has been proved here on the basis of provocation tests in 7 of 8 patients. A challenge was not possible for 1 patient (patient 4) because his parents feared his having the same huge problems as before. Indeed, this boy showed an impressive clinical evolution after the sole withdrawal of potato, with a reduction of the extent score of eczema (score A) from 100 to 22 and of scores B and C from 7 to 3 and from 10 to 3, respectively. Therefore taking this striking improvement together with the clearly positive SPT, potato CAP, and immunoblotting results, we consider allergy to cooked potato also to have been sufficiently demonstrated in this child. Although a striking decrease in the severity of atopic dermatitis could be shown after the elimination of potato from the diets of 6 children, only 3 of them had an eczematous reaction on potato challenge. Probably the challenge dose, duration of the challenge, or both were insufficient to elicit eczema in these children. 22 Five of 7 children had an immediate reaction. The different clini-

528 De Swert, Cadot, and Ceuppens J ALLERGY CLIN IMMUNOL SEPTEMBER 2002 TABLE II. SPTs with homemade and commercial potato extracts Patients Control subjects No. with No. with SPTs positive response No. tested positive response No. tested P value* Cooked extract, 50 or 500 µg/ml Bintje 5 7 0 9 <.005 Charlotte 6 7 0 9 <.001 Bintje or Charlotte 7 7 0 9 <.0001 Noncooked extract, 50 or 500 µg/ml Bintje 7 7 1 8 <.002 Charlotte 7 7 0 4 <.003 Commercial extract 8 8 1 9 <.0004 *Fisher exact test, 2-tailed. cal reaction patterns might be the expression of different pathways of activation, with IgE-mediated mast cell activation in the patients with immediate with activation of low-affinity IgE receptors on eosinophils, a cytokine-induced reaction, or both in patients with latephase effects. The overall reaction profile in a particular patient might be the result of the relative contribution of both mechanisms. 27,28 Because different disease pathways might require different challenge dosages, this might explain the different clinical reactions we observed in our patients. In our study 8 of 8 patient sera recognized several protein bands with molecular masses ranging from 14 to 60 kd in SDS-PAGE immunoblots, which is comparable with the findings of other authors. 7,8,19 Seven of 8 patient sera recognized a double band of approximately 40 kd, which might correspond to Sol t 1 (or patatin), the major allergen of potato. 18 One serum also recognized a protein band of approximately 85 kd, which was not previously recognized by patients in other studies. In this way we have contributed to the completion of the pattern of antigens that might play a role in allergy to cooked potato, even if that particular antigen would be relevant for a subgroup of patients with potato allergy only. Potato CAP values were substantially higher in our patient group compared with values found in patients with positive challenge results and late-phase reactions to potato studied by others. 10 Comparatively high levels of potato-specific IgE were found in the patients with immediate reactions to cooked potato studied by another group. 8 This, together with the observation that our patients, although having eczema in most cases, showed an immediate reaction in 5 of 7 cases when challenged with potato, might indicate that both IgE-mediated and other activation pathways might be involved, as was suggested previously. This is the first study using a cooked potato extract for skin prick testing. Doing so, we excluded skin reactions to heat-labile allergens, and we could demonstrate that cooked potato was able to elicit immediate skin responses in all 7 patients tested. In contrast to other authors, we did not perform a prick-to-prick test with raw potato. 10,18 Indeed, in a preliminary study we have performed prickto-prick tests with raw potato in 5 patients with potato allergy and in 14 age-matched atopic control subjects without any history of allergy to cooked potato (data not shown). Because this test response was positive not only in all patients but also in 7 of 14 control children, we concluded that it was not useful in characterizing the patient group. Because skin prick testing with cooked potato extract provided highly specific results, it provides a useful tool in detecting patients with allergy to cooked potato. 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