D3.219 - Selective Octopus Allergy: A Unique Case Report

Background:

Most shellfish allergic patients report clinical reactivity to several species due to cross-reactivity of tropomyosin. However, to the best of our knowledge, selective allergy to octopus (Octopus vulgaris) has not been previously reported in the scientific literature. 

Methods:

A 77-year-old male experienced an immediate allergic reaction to octopus, presenting with dyspnea, urticaria and angioedema. The patient had tolerated afterwards various shellfish, including bivalves, crustaceans, and other cephalopods like squid and cuttlefish, without reactions. The reaction was confirmed at another hospital through an oral challenge test. Prick-prick test was performed with cooked octopus. Western Blot analysis was performed using octopus protein extract and the patient's serum to detect specific IgE reactivity. Protein identification was carried out via mass spectrometry, using the Uniprot database taxonomically restricted to Octopus vulgaris.

Results:

Prick-prick test with octopus was positive. Total IgE was 739 kU/L, and specific IgE to squid, mussel, lobster, octopus, and anisakis were all negative. Tropomyosin (r Pen a1) was negative. Specific IgE (ImmunoCAP) to Dermatophagoides pteronyssinus, Lepidoglyphus destructor, and Tyrophagus putrescentiae were  0.4, 0.55 and 0.41 KUA/l, respectively. Baseline tryptase was  6.27 ng/mL. IgE reactivity was identified against two distinct protein bands in octopus extracts one at around 75 kDa, and a doublet at 37 kDa. Western blot inhibition with mite extract showed no significant cross-reactivity suggesting a unique allergenic profile specific to octopus proteins. Mass spectrometry analysis revealed that bands at around 37kDa corresponded both to tropomyosin, while the band of 75 kDA was identified as a heavy chain myosin.

Conclusion:

This case highlights a selective allergy to octopus, a rare phenomenon not previously reported. The myosin heavy chain has been previously described as an allergen in crustaceans, gastropods, and mites, but not in cephalopods such as the octopus. The selective allergic reaction to octopus may be due to a tropomyosin and heavy chain myosin specific epitope recognition.