Background: the parasite Anisakis simplex is a helminth included in the nematode class. When man eats raw or rare fish and cephalopods infested by Anisakis larvae, he can acquire the parasitic disease (anisakidosis). The parasite can also originate manifestations of immediate IgE mediated hypersensitivity in patients with sensitisation to it.
Methods and results: we present the case of a 14 year old boy diagnosed of eosinophilic gastritis after endoscopic examination and biopsy associated to recurrent abdominal pain. After allergologic study, a type I hypersensitivity mechanism against Anisakis simplex is confirmed by means of prick test, antigen specific IgE determination and antigen specific histamine release test. Sensitisation against fish proteins is ruled out as well as parasitic infestation.
Conclusions: in this case report we demonstrate a type I hypersensitivity mechanism against Anisakis simplex in a patient diagnosed of eosinophilic gastritis. This can be suspected in cases of gastritis or non filiated enteritis with a torpid evolution following the conventional treatment and especially if the onset of the symptoms is related with the intake of fish. The therapeutic success was reached when fish and shellfish were taken out of the diet. After two years without seafood ingestion our patient is asymptomatic and the allergologic study has been normalised.