Overlaps in shrimp, house dust mite allergies drive respiratory, other symptoms
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Approximately half of a group of patients with IgE sensitization to shrimp also were sensitized to house dust mites, and vice versa, according to a letter published in Clinical and Translational Allergy.
Patients with both sensitizations also were more likely to experience respiratory symptoms, angioedema and airflow limitation, Ida Waern, PhD, of the department of anatomy, physiology and biochemistry at the Swedish University of Agricultural Sciences and a visiting researcher in the department of medical biochemistry and microbiology at Uppsala University, both in Uppsala, Sweden, and colleagues wrote.
The muscle protein tropomyosin (Pen a 1) is the major allergen in shrimp as well as an allergen in house dust mites, with homologous forms in insects and mollusks as well, according to the researchers.
The researchers examined data from 4,593 randomly selected individuals aged 50 to 64 years in the Uppsala cohort of the Swedish CArdioPulmonary bioImage Study drawn from extensive questionnaires, blood sampling, physical exams, lung function tests and imaging.
After defining sensitization as specific IgE of 0.35 kUA/L or higher, the researchers found 253 (5.5%) patients who were sensitized to shrimp, 191 (4.2%) sensitized to house dust mite and 104 (2.3%) sensitized to both.
Specifically, 41% of the patients sensitized to shrimp also were sensitized to mite, whereas 54% of the patients sensitized to mite also were sensitized to shrimp. However, the researchers did not find any significant association between the specific IgE titer against mite and sensitization to shrimp among the patients sensitized to mite.
Sensitization to shrimp and mite both had independent associations with angioedema, wheeze and chronic airflow limitation, after adjustments for age, sex and birch and cat sensitization.
Specifically, significantly more patients sensitized to both shrimp and mite than those sensitized to shrimp alone, mite alone or neither reported angioedema (13.2% vs. 9.7%; 11.4%; 5.2%; P < .0001), wheeze (16.3% vs. 5%; 9.9%; 6.4%; P = .001) and chronic airflow limitation (15.2% vs. 4.8%; 6.1%; 7.4%; P = .02).
Patients with sensitization to both shrimp and mite and significant greater odds ratios for angioedema (OR = 2.28; 95% CI, 1.18-4.39), wheeze (OR = 2.47; 95% CI, 1.36-4.47) and chronic airflow obstruction (OR = 2.03; 95% CI, 1.11-3.71).
Urticaria incidence appeared greater among patients sensitized to mite alone, at 44.9% of this subgroup, as well as those sensitized to shrimp (35.6%), compared with sensitization to neither (26.5%) or both (36.4%; P < .0001). Corresponding odds ratios for urticaria were 1.55 (95% CI, 1.05-2.28) for those sensitized to shrimp alone and 2.19 (95% CI, 1.33-3.6) for those sensitized to mites alone.
Plus, there were independent associations between lower FEV1 (% of predicted) and sensitizations to shrimp and mite at –3.5% (range, –6.5 to –0.5) of predicted units.
Noting these overlaps between shrimp and mite sensitizations, the researchers recommended that patients with symptoms of allergy to one of these allergens should be examined for sensitization and allergy to both.
Perspective
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This is a nice letter highlighting the connection between shrimp and house dust mites via the common protein tropomyosin, which is something well-known to allergists, but likely not known among general doctors. When assessing for shellfish allergy, it is important to also assess for house dust mite and cockroach allergy as well, given this connection and cross reactivity.
These findings also bring to light some data regarding the sensitization of shrimp and/or house dust mite and its impact on asthma. Of particular interest to me was the limitation in lung function when someone is sensitized to both shrimp and house dust mite, raising awareness of not only the shrimp/house dust mite connection but also its ramifications on asthma.
These results are comparable to my experience. I have had several patients who had anaphylaxis while eating shellfish. But when we tested them, they were negative for shellfish but massively positive for house dust mite. They had asthma as well, which also was a serious factor in their episode.
Doctors can use these findings to improve care. First, we need to understand these connections. Second, if someone is presenting with either shellfish or house dust mite allergy, we want to make sure the other is evaluated and at least discussed.
It is important to educate patients about this connection. If they are allergic to both shrimp and house dust mite and have asthma, they need to be very diligent and aggressive in controlling their asthma.
Because shrimp allergy often presents a little later in life, but many people may be sensitized to house dust mite earlier in life, I would love to see studies on allergen-specific subcutaneous or sublingual immunotherapy for house dust mite to see if it can prevent shellfish allergy or at least decrease the prevalence of shellfish allergy in adulthood. I also would like to see studies on the impact of immunotherapy in this population on their asthma.
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