AGA Clinical Practice Update on Alpha-Gal Syndrome for the GI Clinician: Commentary

Postprandial symptoms in disorders of gut-brain interaction and their potential as a treatment target

Postprandial, or meal-related, symptoms, such as abdominal pain, early satiation, fullness or bloating, are often reported by patients with disorders of gut-brain interaction, including functional dyspepsia (FD) or irritable bowel syndrome (IBS). We propose that postprandial symptoms arise via a distinct pathophysiological process. A physiological or psychological insult, for example, acute enteric infection, leads to loss of tolerance to a previously tolerated oral food antigen. This enables interaction of both the microbiota and the food antigen itself with the immune system, causing a localised immunological response, with activation of eosinophils and mast cells, and release of inflammatory mediators, including histamine and cytokines. These have more widespread systemic effects, including triggering nociceptive nerves and altering mood. Dietary interventions, including a diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols, elimination of potential food antigens or gluten, IgG food sensitivity diets or salicylate restriction may benefit some patients with IBS or FD. This could be because the restriction of these foods or dietary components modulates this pathophysiological process. Similarly, drugs including proton pump inhibitors, histamine-receptor antagonists, mast cell stabilisers or even tricyclic or tetracyclic antidepressants, which have anti-histaminergic actions, all of which are potential treatments for FD and IBS, act on one or more of these mechanisms. It seems unlikely that food antigens driving intestinal immune activation are the entire explanation for postprandial symptoms in FD and IBS. In others, fermentation of intestinal carbohydrates, with gas release altering reflex responses, adverse reactions to food chemicals, central mechanisms or nocebo effects may dominate. However, if the concept that postprandial symptoms arise from food antigens driving an immune response in the gastrointestinal tract in a subset of patients is correct, it is paradigm-shifting, because if the choice of treatment were based on one or more of these therapeutic targets, patient outcomes may be improved.

Tick bites, IgE to galactose-alpha-1,3-galactose and urticarial or anaphylactic reactions to mammalian meat: The alpha-gal syndrome

The recent recognition of a syndrome of tick-acquired mammalian meat allergy has transformed the previously held view that mammalian meat is an uncommon allergen. The syndrome, mediated by IgE antibodies against the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal), can also involve reactions to visceral organs, dairy, gelatin and other products, including medications sourced from non-primate mammals. Thus, fittingly, this allergic disorder is now called the alpha-gal syndrome (AGS). The syndrome is strikingly regional, reflecting the important role of tick bites in sensitization, and is more common in demographic groups at risk of tick exposure. Reactions in AGS are delayed, often by 2-6 h after ingestion of mammalian meat. In addition to classic allergic symptomatology such as urticaria and anaphylaxis, AGS is increasingly recognized as a cause of isolated gastrointestinal morbidity and alpha-gal sensitization has also been linked with cardiovascular disease. The unusual link with tick bites may be explained by the fact that allergic cells and mediators are mobilized to the site of tick bites and play a role in resistance against ticks and tick-borne infections. IgE directed to alpha-gal is likely an incidental consequence of what is otherwise an adaptive immune strategy for host defense against endo- and ectoparasites, including ticks.

Recurrent Ogilvie Syndrome as a Possible Manifestation of Alpha-Gal Syndrome (AGS) Requiring Surgical Management: A Case Report

We present a case of a male in his 60s with a history of alpha-gal syndrome (AGS) who presented with recurrent acute colonic pseudo-obstruction, also known as Ogilvie syndrome, and underwent surgical treatment for life-limiting symptoms of colonic distention, constipation, and abdominal pain. Prior to surgery, he was hospitalized multiple times after beef consumption and was diagnosed with Ogilvie syndrome, requiring a colonoscopy with rectal tube placement for symptom resolution. He later underwent a robotic subtotal colectomy with ileocolic anastomosis. Follow-up visits showed improvement in symptoms of constipation and abdominal distention. This case highlights that AGS may lead to severe manifestations, such as recurrent Ogilvie syndrome. Due to the increasing prevalence of AGS and limited data on disease course, further research is needed to determine symptom manifestations and the potential utility of surgery in management.

Food allergies: Updates for nurses

ABSTRACT

Food allergies are on the rise; the incidence and types of foods implicated have increased worldwide. While peanut allergies are the most well-known, allergies exist to almost all types of foods. This article discusses various types of food allergies along with the most recent prevention and treatment strategies.

Allergic reactions associated with medically relevant arthropods

OBJECTIVE

Vector-borne diseases are a growing burden worldwide. In particular, the risks of allergic reactions to bites are associated with growing arthropod populations in contact with the public. The diversity of allergic reactions associated with host and arthropod factors difficult disease diagnosis, prognosis and prevention. Therefore, arthropod-associated allergies are underdiagnosed and require better surveillance of arthropod populations and disease diagnosis and management.

METHODS

To face these challenges, in this study, we describe five cases to illustrate arthropod-associated allergies with different symptomatology, including alpha-gal syndrome (AGS) associated with anti-alpha-gal IgE antibody titres. Information on symptoms in response to arthropod bites was collected from patients and medical doctors.

RESULTS

The five cases included patients bitten by a robber fly and different tick species. Cases were in Spain or U.S.A. Two cases were diagnosed with AGS and one case was diagnosed with anaphylaxis in response to tick bite with high anti-alpha-gal IgE levels. The symptoms in response to arthropod bites vary between different cases.

CONCLUSION

Allergic reactions and symptoms in response to arthropod bites vary in association with host and arthropod factors. Herein we propose recommendations to control allergic symptoms, associated disease risk factors and the way forward to advance in the prevention and control of arthropod-associated allergies.

An outbreak of anaphylactic transfusion reactions to group B plasma and platelets and its possible relationship to Alpha-Gal syndrome

BACKGROUND

Alpha-gal syndrome (AGS) is a potentially life-threatening acquired meat allergy associated with tick bites. The allergen Galactose-α-1,3-Galactose is antigenically similar to the B blood group antigen. B blood group status offers some protection against development of the allergy. Although not preferred practice, transfusion of plasma and platelets from group B donors is believed to be safe for group O recipients.

STUDY DESIGN AND METHODS

Anaphylactic transfusion reactions were reported for three patients in two Washington DC hospitals from Nov 2022 to February 2023. A chart review was performed for all three patients. Patients or family members were interviewed, and IgE levels to alpha-gal were measured in two of the three patients.

RESULTS

One reaction was acutely fatal. All reactions were to blood group B Plasma or Platelets in blood group O recipients. One patient had two prior anaphylactic reactions to group O RBCs and group B Plasma in a previous admission. All patients came from southern Maryland where AGS is an emerging problem. Two patients had histories of tick bites, previously unexplained gastrointestinal complaints, and abnormal elevated levels of IgE to alpha gal. Two patients had cat allergies.

DISCUSSION

AGS is an emerging problem which may have implications for blood transfusion practice. Avoidance of blood group B antigen containing components may be prudent in non-blood group B patients with established AGS. Investigation for AGS should be considered in the evaluation of anaphylactic transfusion reactions.

Health Care Provider Knowledge Regarding Alpha-gal Syndrome - United States, March-May 2022

Alpha-gal syndrome (AGS) is an emerging, tick bite-associated immunoglobulin E-mediated allergic condition characterized by a reaction to the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal), which is found in mammalian meat and products derived from mammals, including milk, other dairy products, and some pharmaceutical products. Symptoms range from mild (e.g., a rash or gastrointestinal upset) to severe (anaphylaxis); onset typically occurs ≥2 hours after exposure to alpha-gal. No treatment or cure is currently available. Despite the potential life-threating reactions associated with AGS, most patients perceive that health care providers (HCPs) have little or no knowledge of AGS. A U.S. web-based survey of 1,500 HCPs revealed limited knowledge of AGS, identified areas for continuing medical education, and described self-reported diagnostic and management practices. Overall, 42% of surveyed HCPs had never heard of AGS, and among those who had, fewer than one third knew how to diagnose the condition. Two thirds of respondents indicated that guidelines for the diagnosis and management of AGS would be useful clinical resources. Limited awareness and knowledge of AGS among HCPs likely contributes to underdiagnosis of this condition and inadequate patient management, and underestimates of the number of AGS patients in the United States, which currently relies on laboratory testing data alone.

Alpha-Gal Sensitization in a US Screening Population Is Not Associated With a Decreased Meat Intake or Gastrointestinal Symptoms

INTRODUCTION

Patients with alpha-gal syndrome, a delayed reaction to mammalian meat, can present with isolated gastrointestinal (GI) symptoms. We aimed to estimate the frequency of alpha-gal sensitization in a Southeastern US population and determine the association between sensitization and mammalian product dietary intake or GI symptoms.

METHODS

We performed a cross-sectional study of participants who underwent a screening colonoscopy at our center between 2013 and 2015. We quantified serum alpha-gal immunoglobulin E antibodies in participants who were prospectively enrolled at screening colonoscopy and compared diet intake and lower GI symptoms reported in standardized questionnaires among those with elevated versus no alpha-gal IgE antibodies.

RESULTS

Alpha-gal IgE antibodies were common-31.4% of screening colonoscopy participants (127 of 404) had elevated serum alpha-gal IgE >0.1 kU/L. Alpha-gal-sensitized participants endorsed similar rates of abdominal pain compared with those without alpha-gal antibodies (33% vs 38%, adjusted odds ratio 0.9, 95% confidence interval 0.7-1.3). Mammalian meat consumption did not differ based on alpha-gal sensitization status (average 1.43 servings/d in sensitized subjects vs 1.50 in alpha-gal IgE-negative subjects, P = 0.9). Alpha-gal-sensitized participants with levels ≥10 (n = 21) were overrepresented in the lowest quartiles of mammalian meat consumption, but not among those with GI symptoms in general. Participants with high alpha-gal antibody levels >2 kU/L (n = 45) or ≥10 U/L (n = 21) did not have a reduced mean daily mammalian meat intake compared with seronegative people.

DISCUSSION

Elevated alpha-gal IgE antibodies were common and not associated with a reduced mammalian meat intake, abdominal pain, or diarrhea. Seropositivity did not predict symptomatic alpha-gal sensitization in this general screening population. Other host factors likely contribute to the phenotypic expression of alpha-gal syndrome.