Rosaceae-associated exercise-induced anaphylaxis with positive SPT and negative IgE reactivity to Pru p 3.

BACKGROUND Food-dependent-exercise-induced anaphylaxis (FDEIA) is characterized by anaphylactic symptoms after exercise following ingestion of food. We present a case of FDEIA induced by Rosacee fruits showing some diagnostic problems. MATERIAL AND METHODS A 12 years-old boy with seasonal allergy to olive and cypressus pollens, experienced two distinct episodes of FDEIA, grade 4 and 3 of the Sampson Scale respectively, during intense exercise, about 30 minutes after eating a peach with peel or some cherries. SPT with commercial peach extract and fresh Rosacee fruits scored positive while SPT with a date palm profilin-enriched extract was negative. On in vitro tests total IgE were 44 kU/l and IgE for peach, cherry, Prup 3, Prup 1, Bet v 1, Bet v 2, Bet v 4 were negative. SPT with Prup 3 UniCAP device (cellulose polymer in a plastic reserve highly binding allergen protein) was negative. An oral food challenge, performed at rest using a commercial peach juice, scored negative. An immunoblot analysis performed with peach extract was negative. DISCUSSION The main peculiarity of this case of FDEIA is the discrepancy between positive SPT and negative in-vitro findings. The positive SPT with the commercial peach extract suggested hypersensitivity to lipid transfer protein; however, no IgE reactivity to rPrup 3 was found in-vitro. The negative immunoblot analysis, possibly caused by the low levels of specific IgE, did not allow us to investigate the nature of the relevant allergen protein further. It is possible that this patient reacted to a different peach allergen or, alternatively, that he recognized an isoform of LTP that is different fr-om that in Uni-CAP. CONCLUSION This case emphasizes once more the diagnostic relevance of SPT with extracts and fresh material to be performed before investigating IgE reactivity to single allergen components in-vitro.