“Also, it’s striking how many patients develop palmar erythema and itching during an episode. Not all report it, but when they do it’s usually a pretty good giveaway that they might have IgE to alpha-gal,” according to the allergist.
He added that it’s entirely reasonable to order a screening test for IgE to alpha-gal in patients in lone star tick–abiding states whose anaphylactic reactions seem to occur randomly without an apparent trigger.
Dr. Commins and his coinvestigators have assembled a database of roughly 500 of their patients with IgE to alpha-gal, about half of whom have a history of atopy. The investigators have found that an individual’s atopic status has no bearing on IgE antibody titer or the severity of the delayed reactions. Moreover, neither the alpha-gal IgE antibody level, the ratio of alpha-gal-specific IgE to total IgE, nor IgG antibodies correlate with reaction severity, he continued.
Based upon their study of 45 affected children, Dr. Commins and coworkers concluded that the clinical presentation and serum IgE pattern are the same as in adults (Pediatrics 2013 May [doi:10.1542/peds.2012-2585]). Since that publication, however, the investigators have realized there is a subgroup of affected teenagers who present with GI symptoms, he added.
Turning to disease management, Dr. Commins said he advocates an avoidance diet that eliminates mammalian meats, rich desserts, and super-premium ice cream.
“I also counsel patients to avoid broths, gravies, and anything that might be a mystery sauce,” he said. “You’d be surprised at how many people with alpha-gal order chicken at a Mexican restaurant thinking that they’re doing the right thing and end up reacting. I don’t know exactly why it happens, so I just say ‘avoid mystery sauces.’ Dairy and cheese are actually fairly well tolerated, although soft cheeses, like brie, can cause a reaction.”
Reactions are inconsistent, and symptoms can vary from episode to episode. Cofactors are a concern, with exercise and alcohol tending to make patients more sensitive to an alpha-gal exposure. The degree of risk posed by vaccines containing gelatin constitutes an emerging and unresolved issue.
“We’ve heard of several reactions to the shingles vaccine because of the gelatin, and the MMR vaccine is also on the radar,” Dr. Commins said.
Implantation of porcine bioprosthetic heart valves in patients with serum IgE antibodies to alpha-gal has been associated with reports of early valve failure; all bioprosthetic valves contain alpha-gal unless they’ve been decellularized. In addition, Dr. Commins is familiar with a case at another university in which three separate attempts to place a bioprosthetic ligament during repeated arthroscopic knee surgeries failed in a patient who had a “screamingly high” level of IgE to alpha-gal.
“I think this bioprosthesis issue is yet to be resolved,” he added.
One audience member, a Texas allergist, said she has a lot of trouble convincing her patients who are avid hunters to give up eating red meats. Dr. Commins said he faces the same issue.
“There is a recalcitrant group that just wants to eat a side of beef every day. I tell them if you’re not going to be on an avoidance diet, at least avoid the fattier cuts and don’t eat tremendous amounts. We believe that the antigen is possibly a glycolipid. Those cuts of meat that are high in fat are the ones patients tell us over and over again give them the worst reactions,” he said.
“The inconsistency of the allergic reactions keeps some patients from taking this disease seriously,” the allergist added. “What eventually happens for some patients is they end up having a really bad reaction. And then that convinces them.”
He monitors affected patients’ alpha-gal IgE levels over time. If and when the IgE becomes negative, he recommends a food challenge test. The patient comes in at 8 a.m., eats three pork sausage patties, and spends the day under observation at the clinic, walking the stairs periodically since exercise is a cofactor. If the challenge goes off without a hitch, the patient is free to go home at 4 or 5 p.m. In the past, that was the patient’s ticket to clearance to safely eat a big meat meal with alcohol, but Dr. Commins has pulled back of late from that recommendation.
“We believe that additional tick bites can make the allergy come back. So if someone passes a challenge in October and then the following spring gets more tick bites, you may have set them up to have a reaction because you’ve told them they can eat meat again. So the utility of a negative food challenge is unclear unless you’re pretty confident a patient is not going to have more tick bites,” he explained.