Scallop

 
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Code: f338
Latin name: Pecten spp.
Source material: Muscle
Family: Pectinidae
Genus: Pecten
Phylum: Mollusca
Class: Bivalviar
Order: Pterioida

Allergen Exposure

Scallops, or fan shells, are found in all seas, shallow as well as deep. Adult scallops are usually free-swimming. The well-developed muscle is the food served as scallop or, in France Coquille St. Jacques.

Potential Cross-Reactivity

Cross-reactivity between crustaceans and mollusks has been demonstrated (1-3). Immunoblot inhibitions have demonstrated up to 28% bi-directional cross-reactivity between shrimp and scallops, further confirming the major cross-reactive antigen as the respective tropomyosins of shrimps and scallops (2).

Many patients allergic to shrimp do not show clinical hypersensitivity reactions to mollusks or other seafood, thus indicating the existence of genus specific antigens. Cross-reactivity could thus not be demonstrated between squid and octopus, which are both cephalopods, or between squid and other mollusks (4).

Clinical Experience

Many common types of seafood have been reported to be involved in allergic diseases, with reactions including urticaria, angioedema, gastrointestinal distress, asthma, rhinitis and anaphylaxis (1, 5-7). Severe adverse reactions to scallops have been described, requiring emergency treatment (8).
 
Review
The phylum Mollusca includes among its about 100,000 living forms several important seafoods: clams, mussels, oysters and scallops (Bivalvia), snails, abalone (Gastropoda), and squid, cuttlefish and octopus (Cephalopoda).
Scallops, or fan shells, are found in all seas, shallow as well as deep. Adult scallops are usually free-swimming. The well-developed muscle is the food served as scallop or, in France Coquille St. Jacques.
 
Many common types of seafood have been reported to be involved in allergic diseases, with reactions including urticaria, angioedema, gastrointestinal distress, asthma, rhinitis and anaphylaxis (1, 5-7). Severe adverse reactions to scallops have been described, requiring emergency treatment (8). Occupational asthma was reported in a seafood restaurant worker, with independent hypersensitivity to both shrimp and scallops (2). Preparing seafood while working near boiling vats of seafood, the patient was most likely exposed to high concentrations of allergen aerosols (7).
 
Cross-reactivity between crustaceans and mollusks has been demonstrated (1-3).
Immunoblot experiments with sera from 9 subjects with a clinical history of hypersensitive reactions to shrimp showed cross-reactivity against 10 common edible mollusks (1). All sera showed IgE activity to a 38kD protein present in boiled muscle extracts of all mollusks. The results suggest that the heat-stable 38kD protein is the major cross-reactive allergen present in crustaceans and mollusks, earlier identified as the muscle protein tropomyosin (9, 10). Immunoblot inhibitions have demonstrated up to 28% bi-directional cross-reactivity between shrimp and scallops, further confirming the major cross-reactive antigen as the respective tropomyosins of shrimps and scallops (2). The additional finding of less extensive inhibition of 21kD and 26kD shrimp proteins by scallops supports the existence of more than one cross-reactive allergen between these species. It has, however, been noted that many patients allergic to shrimp do not show clinical hypersensitivity reactions to mollusks or other seafood, thus indicating the existence of genus specific antigens. Cross-reactivity could thus not be demonstrated between squid and octopus, which are both cephalopods, or between squid and other mollusks (4).
 
The frequent hypersensitivity to seafoods and the severe reactions occasionally associated with different mollusks, including scallop, warrants the use of IgE antibody tests for a correct diagnosis and a recommendation of avoidance of the offending agent.

References

  1. Leung PSC, Chow WK, Duffey S, Kwan HS, Gershwin ME, Chu KH. IgE reactivity against a cross-reactive allergen in crustacea and mollusca: Evidence for tropomyosin as a common allergen. J Allergy Clin Immunol 1996;98:954-61.
  2. Goetz DW, Whisman BA. Occupational asthma in a seafood restaurant worker: cross-reactivity of shrimp and scallops. Ann Allergy Asthma Immunol 2000;85:461-66.
  3. Goetz DW, Whisman BA. Cross-reactive allergens of shrimp and scallops identified by ELISA and immunoblot inhibitions. J Allergy Clin Immunol 1990;85:531.
  4. Carillo T, Castillo R, Caminero J, Cuevas M, Rodriguez JC, Acosta O et al. Squid hypersensitivity: a clinical and immunologic study. Ann Allergy 1992;68:483-87.
  5. Daul CB, Morgan JE, Lehrer SB. Hypersensitivity reactions to Crustacea and Mollusks. Clin Rev Allergy 1993;11:201-22.
  6. Castillo R, Carrilo T, Bianco, Quiralte J, Cuevas M. Shellfish hypersensitivity: Clinical and immunological characteristics. Allergol et Immunopathol 1994;22:83-7.
  7. Desjardins A, Malo J-L, L´Archevêque J, Cartier A, McCants M, Lehrer SB. Occupational IgE-mediated sensitization and asthma caused by clam and shrimp. J Allergy Clin Immunol 1996;96:5.
  8. Bock SA, The incidence of severe adverse reactions to food in Colorado.
    J Allergy Clin Immunol 1992;90:683-85.
  9. Shanti KN, Martin BM, Nagpal S, Metcalfe DD, Rao PV. Identification of tropomyosin as the major shrimp allergen and characterization of its IgE binding epitopes. J Immunol 1993;151:5354-63.
  10. Leung PS, Chu KU, Chow WK, Ansari A, Bandea CI, Kwan HS et al. Cloning, expression and primary structure of Metapenaeus ensis tropomyosin, the major heat-stable shrimp allergen. J Allergy Clin Immunol 1994;94:882-90.

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.