American Academy of Allergy, Asthma & Immunology, March 2-5
The annual meeting of the American Academy of Allergy, Asthma & Immunology was held from March 2 to 5 in Orlando, Fla., and attracted more than 5,000 participants from around the world, including clinicians, academicians, allied health professionals, and others interested in recent advances in allergy, asthma, and immunology.
In one study, Jonathan R. Brestoff, M.D., Ph.D., of the Washington University School of Medicine in St. Louis, and colleagues found that a patient's blood type appears to alter susceptibility to developing an allergy to red meat.
"Red meat allergy is a recently described food allergy characterized by anaphylaxis or other allergic reactions occurring about three to six hours after ingesting red meat products containing galactose-α-1, 3-galactose (alpha-gal)," Brestoff said. "The structure of alpha-gal is very similar to the B antigen of the ABO blood group system, so we wondered whether patients with blood types B or AB are tolerant to alpha-gal and therefore protected from developing red meat allergy."
The investigators compared 92 red meat allergy patients and 188 patients without the sensitivity.
"We were amazed to find that patients who express the B antigen (blood types B or AB) are five times less likely to undergo allergic sensitization to alpha-gal and five times less likely to develop red meat allergy than patients who do not express this factor (blood types O or A)," Brestoff said. "We recommend that patients being evaluated for red meat allergy should have their blood type documented because the results of blood typing directly impact the interpretation of commonly employed diagnostic tests for red meat allergy, such as alpha-gal immunoglobulin E testing."
In another study, Emily McGowan, M.D., of the University of Virginia in Charlottesville, and colleagues found that higher levels of the synthetic folic acid derivative -- unmetabolized folic acid (UMFA) -- is associated with the development of food allergy.
"Folate (vitamin B9) is available in either the natural or synthetic forms and has been shown to reduce the risk of neural tube defects in newborns. Folic acid, the synthetic form of folate, is widely consumed in the United States in infant formula, supplements, vitamins, and fortified grains," McGowan said. "When folic acid is consumed in high quantities, some of it does not undergo further metabolism and circulates in the blood as UMFA."
The investigators measured total folate, UMFA, and 5-methyltetrahydrofolate (5-MTHF), the main folate metabolite involved in biochemical processes in the body, in a subset of children from the Boston Birth Cohort.
"While mean levels of total folate at birth were lower among those who developed food allergy, mean levels of UMFA were higher. There was no association between total folate, 5-MTHF, or UMFA levels in early life and the development of food allergy," McGowan said. "At this time, we do not recommend any changes to current clinical practice. More research is needed to determine whether mothers should consume different sources of folate, such as green leafy vegetables, beans, and lentils during pregnancy instead of synthetic folic acid."
Corinne Keet, M.D., Ph.D., of John Hopkins Medicine in Baltimore, and colleagues found that milk allergy is associated with decreased weight and height growth velocity in childhood.
"We examined children with milk allergy and compared their growth to children who were only avoiding peanuts and/or tree nuts. We found that those who were avoiding milk not only had lower weight and height on average, but that these differences increased over time," Keet said. "These results emphasize that providers should be monitoring milk allergic children for nutritional status and growth. Milk avoidance can have significant nutritional impacts."
Philip L. Lieberman, M.D., of Allergy and Asthma Care in Germantown, Tenn., and colleagues identified an increase in anaphylaxis cases caused by alpha-gal, which is associated with red meat allergy.
"Our review of patients with anaphylaxis dates back to 1978. All of these investigations were designed to characterize the nature of anaphylactic events in adults and adolescents. The purpose of our most recent retrospective review was to see if the nature of such events had changed since our last report which was in 2006," Lieberman said. "In our present report, we found two significant changes in the nature of events that have affected the way we evaluate and treat patients who have experienced anaphylaxis. These changes were prompted by two discoveries made since our last review. These were: (1) the discovery of anaphylaxis related to tick bites that caused an allergy to alpha gal, which is present in all mammalian meat; and (2) findings that unexplained anaphylaxis can be due to mast cell-related disorders."
Prior to these discoveries, 59 percent or more of patients had idiopathic anaphylaxis. After the discovery of alpha gal allergy and mast cell-related disorders, the investigators identified that the incidence of idiopathic anaphylaxis was reduced to 34 percent.
"Because of these findings, additional tests were added to our standard work-up of a patient presenting with anaphylaxis. The tests that were added to detect these conditions were specific immunoglobulin E in the blood to alpha gal and a serum tryptase, along with a mutational analysis for a tyrosine kinase receptor, on the surface of the mast cell to detect mast cell-related disorders. All three of these tests are done on blood and are commercially available," Lieberman said. "The detection of either alpha gal sensitivity or a mast cell-related disorder can alter how the patient is treated. In the former, episodes can be totally prevented by avoidance of mammalian meat and other foods containing alpha gal (e.g., gelatin). And in the latter, medications such as omalizumab and in some cases tyrosine kinase receptor inhibitors can be employed."