Clinical features of four cases with cashew nut allergy and cross-reactivity between cashew nut and pistachio.

BACKGROUND

Few cases of cashew nut (CN) allergy have been reported in Japan. We evaluated the clinical features of 4 cases with CN allergy and investigated the allergens involved.

METHODS

In order to investigate the cross-reactivity between CN and pistachios, we performed ImmunoCAP inhibition tests using sera of 4 cases with positive histories of CN allergy and positive results of specific IgE measurement (ImmunoCAP) and skin prick tests. Furthermore, we analyzed the molecular weights of allergens of CN and pistachios by IgE-immunoblotting.

RESULTS

Of the 4 cases (male : female = 1:3), there were 3 cases (patient #2-4) and 1 case (patient #1) of anaphylaxis and oral allergy syndrome, respectively. The initial symptom was an oropharyngeal symptom in 3 of the 4 cases, of which 2 cases developed anaphylaxis within 10 minutes after eating only a few pieces of CN. All 4 cases reacted positively to the skin prick test with CN, although 1 case of anaphylaxis tested negatively for CN by ImmunoCAP. Additionally, in 2 cases, IgE-binding to CN and pistachio were inhibited with both pistachios and CN, indicating cross-reactivity between CN and pistachios. IgE-immunoblotting of CN using sera from the 4 cases revealed 2 bands at molecular weights of approximately 33 kd and 42 kd, whereas that of pistachios showed a single band at 36 kd. However, IgE in all 4 sera did not bind to rAna o 2.

CONCLUSIONS

In CN allergy, a small amount of CN could induce a severe anaphylactic reaction. Moreover, in cases of suspected CN allergy, reactions to not only CN but also pistachio, which could be cross-reactive to CN, should be examined.