D2.93 - The role of tropomyosins in allergenic cross-reactivity

Tropomyosin is a panallergen that is localized in both crustaceans, house dust mites and cockroaches, due to the similarity of amino acid sequences, with significant thermal stability. Additionally, tropomyosin has a very high degree of IgE cross-reactivity between aeroallergens and food allergens, being presented in the structure of other allergens (mites, cockroaches, worms) as a cross-reactive protein. It is responsible for moderate to severe clinical manifestations in food exposures (food allergy to mollusks and crustaceans) or mild manifestations in exposure to dust mites.

We present a 40-year-old patient with symptoms of rhinoconjunctivitis associated with urticaria after exposure to dust mites. Lip angioedema and hives after eating shellfish and mollusks, after 20 minutes. Serological testing of specific immunoglobulin E test of molecular allergens determines sensitivity to tropomyosin fish and seafood (Pen m 1 = 7.71 kUA/L; Pen m 2, Cra c 6 –Troponin C = 8.02; Hom g, Lit s, Lol spp., Myt e, Ost e, Pan b, Pec spp., Rud spp., Ach d; Loc m; Ten m, Ani s 3 = 7.98;), cockroach (Per a 7 = 8.75 kUA/L; Bla g 9 = 8.16 kUA/L); dust mites (Der p 10 = 10.10 kUA/L; Blo t 10 = 11.51 kUA/L). The patient also shows sensitivity to pollen Amb a 1 = 17.17 kUA.

Polysensitization to tropomyosins from different allergenic sources may be present in patients with seafood allergies. Cross-reactivity with tropomyosins from respiratory allergen sources can induce mixed symptoms (respiratory, skin). The risk of severe reactions remains due to the thermostability of the protein; therefore, avoiding exposure to seafood is important.

Exposure to sources of tropomyosin in beetles and insects, although unintentional, may occur through the consumption of cereals or the contamination of plant-based foods.

Treatment with antihistamines, intranasal corticosteroids, and avoidance of exposure to shellfish allowed control of the symptoms of rhinoconjunctivitis and urticaria. Understanding the mechanism is crucial for correctly interpreting sensitizations and assessing patient risk.