Cross-reactivity between buckwheat and quinoa in a patient with eosinophilic esophagitis caused by wheat.

Eosinophilic esophagitis is a chronic, antigen-mediated esophageal disease characterized clinically by symptoms of esophageal dysfunction and histologically by eosinophilpredominant inflammation. The symptoms of eosinophilic esophagitis in adults are (from the least to the most frequent) dysphagia, chest pain, food impaction, and upper abdominal pain [1]. We present the case of a 38-year-old woman with intolerance to nonsteroidal anti-inflammatory drugs (NSAIDs), rhinoconjunctivitis caused by grass pollen, and recently diagnosed eosinophilic esophagitis caused by flour (wheat and other). After following a flour-free diet, the patient was asymptomatic, and biopsy studies revealed no eosinophilic inflammation. As the patient suggested the possibility of consuming products containing buckwheat flour (Fagopyrum esculentum) and quinoa seed flour (Chenopodium quinoa), neither of which she had eaten before, a sensitization study was performed. The patient was asked to avoid both foods until the study was complete. Extracts from quinoa seed and buckwheat flour were prepared by homogenization in phosphate buffer saline, dialyzation, and lyophilization. Both were diluted in phenol glycerol saline solution at a concentration of 20 mg/mL, and skin prick tests (SPT) were performed with standardized lancets. The results were positive for both extracts. The results of SPT with buckwheat flour and quinoa extracts were negative in 10 controls (5 nonatopic controls and 5 atopic). Serum specific IgE was measured using the enzyme allergosorbent test with quinoa seed (0.8 kUA/L), buckwheat flour (0.8 kUA/L), wheat seed (1.6 kUA/L), wheat flour (0.6 kUA/L), rice flour (0.9 kUA/L), and soybean (0.7 kUA/L). SDS-PAGE immunoblotting with extracts of quinoa and flours from buckwheat, wheat, and rice was performed following the Laemmli method. After incubation of the polyvinylene difluoride membrane with the patient’s serum, IgE binding bands of 28-30 kDa and 45-50 kDa were detected in all of Figure. SDS-PAGE immunoblotting results. A, Quinoa extract. B, Buckwheat flour extract. C, Wheat flour extract. D, Rice flour extract. Lane P, patient serum; Lane C, control serum (pool of sera from nonatopic patients); Lane M, molecular mass marker. the assayed extracts (Figure). Both bands were previously described by Park et al [2]. The first band could correspond to Fag e 1, a legumin of 11S-type globulins, although this allergen is a 24-kDa protein. The second could be Fag e 3, a 7S-vicilin–like globulin. Both are present in soybean. Crossreactivity has been detected between 2S, 7S, and 11S-globulins of soybean [3]. No allergens have been described for C quinoa flour. Immunoblot-inhibition assays with extracts of quinoa and buckwheat in the solid phase revealed the existence of cross-reactivity between proteins from both extracts and between these proteins and others from wheat and rice flour extracts (results not shown). Consequently, the patient was also instructed to avoid buckwheat flour and quinoa. Three months later, biopsy studies showed no eosinophilic inflammation at all, and the patient continues to avoid dairy products containing flours, quinoa, and buckwheat.