Anaphylaxis is the most serious of all allergic reactions and can be fatal. The diagnosis is frequently delayed, and misdiagnosis often occurs with asthma or urticaria. Biomarkers such as tryptase are not routinely checked, and appropriate treatment with epinephrine is not administered in a majority of cases, increasing the risk of poor outcomes. The objective of this review is to provide a better understanding of the pathophysiology of anaphylaxis with a description of phenotypes, endotypes, and biomarkers available in both the clinical and research settings. Expanding knowledge with regard to the presentation, causes, and triggers for anaphylaxis among health care providers will improve its diagnosis and management, increase patient safety, and decrease morbidity and mortality.

Drug hypersensitivity reactions (HSRs) are increasing in the 21st Century with the ever expanding availability of new therapeutic agents. Patients with cancer, chronic inflammatory diseases, cystic fibrosis, or diabetes can become allergic to their first line therapy after repeated exposures or through cross reactivity with environmental allergens. Avoidance of the offending allergenic drug may impact disease management, quality of life, and life expectancy. Precision medicine provides new tools for the understanding and management of hypersensitivity reactions (HSRs), as well as a personalized treatment approach for IgE (Immunoglobuline E) and non-IgE mediated HSRs with drug desensitization (DS). DS induces a temporary hyporesponsive state by incremental escalation of sub-optimal doses of the offending drug. In vitro models have shown evidence that IgE desensitization is an antigen-specific process which blocks calcium flux, impacts antigen/IgE/FcεRI complex internalization and prevents the acute and late phase reactions as well as mast cell mediator release. Through a “bench to bedside” approach, in vitro desensitization models help elucidate the molecular pathways involved in DS, providing new insights to improved desensitization protocols for all patients. The aim of this review is to summarize up to date information on the drug HSRs, the IgE mediated mechanisms of desensitization, and their clinical applications.

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Multistep mast cell desensitization blocks the release of mediators following IgE crosslinking with increasing doses of Ag. Although its in vivo application has led to the safe reintroduction of drugs and foods in IgE-sensitized patients at risk for anaphylaxis, the mechanisms of the inhibitory process have remained elusive. We sought to investigate the kinetics, membrane, and cytoskeletal changes and to identify molecular targets. IgE-sensitized wild-type murine (WT) and FcεRIα humanized (h) bone marrow mast cells were activated and desensitized with DNP, nitrophenyl, dust mites, and peanut Ags. The movements of membrane receptors, FcεRI/IgE/Ag, actin, and tubulin and the phosphorylation of Syk, Lyn, P38-MAPK, and SHIP-1 were assessed. Silencing SHIP-1 protein was used to dissect the SHIP-1 role. Multistep IgE desensitization of WT and transgenic human bone marrow mast cells blocked the release of β-hexosaminidase in an Ag-specific fashion and prevented actin and tubulin movements. Desensitization was regulated by the initial Ag dose, number of doses, and time between doses. FcεRI, IgE, Ags, and surface receptors were not internalized during desensitization. Phosphorylation of Syk, Lyn, p38 MAPK, and SHIP-1 increased in a dose–response manner during activation; in contrast, only SHIP-1 phosphorylation increased in early desensitization. SHIP-1 phosphatase function had no impact on desensitization, but silencing SHIP-1 increased β-hexoxaminidase release, preventing desensitization. Multistep IgE mast cell desensitization is a dose- and time-regulated process that blocks β-hexosaminidase, impacting membrane and cytoskeletal movements. Signal transduction is uncoupled, favoring early phosphorylation of SHIP-1. Silencing SHIP-1 impairs desensitization without implicating its phosphatase function.

RATIONALE: To understand the regulation of IgE production in the recently described alpha-gal mammalian meat food allergy, we have focused on IgE-expressing (IgE +) B cells. These cells typically circulate in low abundance and are generally difficult to detect. Recent improvements in technical methods have made their analysis more feasible. Once identified, we asked whether circulating alpha-gal-specific IgE + B cell populations were affected by ongoing dairy consumption as others have shown that B cell receptor (BCR) signaling negatively regulates IgE responses. METHODS: PBMCs were isolated from controls and subjects with alphagal allergy and stained for surface markers CD19, CD38, CD27, CD138, and membrane IgM, IgG, IgD and IgE as well as fluorochrome-labeled alpha-gal. RESULTS: IgE + B cells that also stained positive for alpha-gal were identified in five subjects allergic to mammalian meat. These alpha-gal-specific IgE + B cells were absent in controls. Of total stained singlet cells, the population of alpha-gal-specific IgE + B cells was 0.092% (median) with a range of 0.013% to 0.15%. There was no association of alpha-gal-specific IgE + B cell frequency with reported severity of allergic reactions. Interestingly, subjects reporting ongoing consumption of alpha-gal antigen in dairy form had generally higher proportion of antigen-specific IgE + B cells. CONCLUSIONS: We have reproducibly identified circulating antigenspecific IgE + B cells in adult subjects with alpha-gal mammalian meat food allergy. Although BCR signaling is thought to negatively regulate IgE responses, our data suggest ongoing dietary antigen exposure is associated with increased numbers of antigen-specific IgE + B cells. Future studies will track these double-positive B cells longitudinally to assess the impact of additional tick bites.

Glycogen hepatopathy (GH) is a rare complication of type 1 diabetes mellitus that leads to an abnormal accumulation of glycogen in the hepatocytes. The exact mechanism of GH remains unknown, but fluctuations in blood glucose and insulin levels play important roles in promoting glycogen accumulation. We report a case of a 16-year-old female diagnosed with poorly controlled type 1 diabetes mellitus with hepatomegaly and elevated liver enzymes. The patient experienced multiple admissions for diabetic ketoacidosis, and she also had celiac disease diagnosed 2 years previously based on serology and a duodenal biopsy. The laboratory analyses results were compatible with acute hepatitis, and the celiac serology was positive. Other investigations ruled out viral hepatitis and autoimmune and metabolic liver diseases. Ultrasound and computerized tomography (CT) scans of the abdomen revealed liver enlargement with diffuse fatty infiltration. A liver biopsy revealed the presence of abundant glycogen in the cytoplasm of the hepatocytes. PAS staining was strongly positive, which confirmed the diagnosis of GH. There were no features of autoimmune hepatitis or significant fibrosis. Duodenal biopsy results were consistent with celiac disease. Despite our efforts, which are supported by a multidisciplinary team approach that included a hepatologist, a diabetic educator, a dietitian, and an endocrinologist, we have encountered difficulties in controlling the patient’s diabetes, and she persistently maintains symptomatic hepatomegaly and abnormal liver biochemistry. Given the patient’s age, we assumed that these abnormalities were related to patient noncompliance. In conclusion, GH remains an under-recognized complication of type 1 DM that is potentially reversible with adequate glycemic control. The awareness of GH should prevent diagnostic delay and its implications for management and the outcome.

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