Lymphocyte subsets and activation markers in patients with acute episodes of idiopathic anaphylaxis

Disease Spectrum of Anaphylaxis Disorders

Anaphylaxis results from massive mast cell activation. Mechanisms of mast cell activation may involve IgE- and non-IgE-mediated triggers, clonal mast cell disease, or be idiopathic and may be modified by several factors including but not restricted to hormonal status, stress, heritable factors, mast cell burden, and simultaneous exposure to more than 1 factor. Patients with recurrent anaphylaxis with a nonidentifiable trigger present a particular challenge in diagnosis and management. Presence of clonal disease may be suggested by hypotensive episodes with urticaria and angioedema, and high baseline tryptase levels. A number of scoring systems have been developed to identify patients who are at high risk to have underlying mastocytosis. This review provides an overview of anaphylaxis disorders and our current understanding of their mechanisms of action, evaluation, and management.

Mastocytosis and Mast Cell Activation Disorders: Clearing the Air

Mast cells are derived from hematopoietic stem cell precursors and are essential to the genesis and manifestations of the allergic response. Activation of these cells by allergens leads to degranulation and elaboration of inflammatory mediators, responsible for regulating the acute dramatic inflammatory response seen. Mast cells have also been incriminated in such diverse disorders as malignancy, arthritis, coronary artery disease, and osteoporosis. There has been a recent explosion in our understanding of the mast cell and the associated clinical conditions that affect this cell type. Some mast cell disorders are associated with specific genetic mutations (such as the D816V gain-of-function mutation) with resultant clonal disease. Such disorders include cutaneous mastocytosis, systemic mastocytosis (SM), its variants (indolent/ISM, smoldering/SSM, aggressive systemic mastocytosis/ASM) and clonal (or monoclonal) mast cell activation disorders or syndromes (CMCAS/MMAS). Besides clonal mast cell activations disorders/CMCAS (also referred to as monoclonal mast cell activation syndromes/MMAS), mast cell activation can also occur secondary to allergic, inflammatory, or paraneoplastic disease. Some disorders are idiopathic as their molecular pathogenesis and evolution are unclear. A genetic disorder, referred to as hereditary alpha-tryptasemia (HαT) has also been described recently. This condition has been shown to be associated with increased severity of allergic and anaphylactic reactions and may interact variably with primary and secondary mast cell disease, resulting in complex combined disorders. The role of this review is to clarify the classification of mast cell disorders, point to molecular aspects of mast cell signaling, elucidate underlying genetic defects, and provide approaches to targeted therapies that may benefit such patients.

Idiopathic Anaphylaxis: A Diagnosis of Exclusion

We report the case of a 67-year-old female with hypertension and rheumatoid arthritis who had 5 unprovoked episodes of anaphylaxis in an 18-month period of time. We review idiopathic anaphylaxis, including its definition, diagnostic work-up, and differential diagnosis.

Idiopathic Anaphylaxis: A Form of Mast Cell Activation Syndrome

Idiopathic anaphylaxis is a condition caused by paroxysmal episodes of sudden-onset multiorgan involvement variably including laryngeal edema, urticaria, bronchoconstriction, dyspnea, hypoxia, abdominal pain, nausea, vomiting, diarrhea, and hypotension. Rarely, the episodes can lead to cardiovascular collapse and death in the absence of a clear trigger, especially in the presence of other cardiovascular comorbidities. Elevated mast cell mediators such as tryptase and histamine have been reported during episodes, and mast cells are considered the primary cells responsible for driving anaphylaxis in humans. Basophils also secrete histamine and LTC4 when activated and theoretically can contribute to symptoms. As our understanding of mast cell disorders continue to grow, the classification for these disorders evolves. The purpose of this article was 2-fold: to review the epidemiology, clinical manifestations, and diagnosis of idiopathic anaphylaxis and to discuss the classification of idiopathic anaphylaxis within the broader context of mast cell activation disorders.

Idiopathic Anaphylaxis: a Perplexing Diagnostic Challenge for Allergists

PURPOSE OF REVIEW

The aim of this systematic review is to present the proposed theories of pathogenesis for idiopathic anaphylaxis (IA), to discuss its classification, its diagnostic approach, and management.

RECENT FINDINGS

IA represents a major diagnostic challenge and is diagnosed when excluding the possible identifiable triggers of anaphylaxis. The current research, however, revealed that certain conditions including mastocytosis, mast cell activation syndromes, and hereditary alpha tryptasemia can masquerade and overlap with its symptomatology. Also, newly identified galactose-alpha-1,3-galactose mammalian red meat allergy has recently been recognized as underlying cause of anaphylaxis in some cases that were previously considered as IA. IA comprises a heterogenous group of conditions where, in some cases, inherently dysfunctional mast cells play a role in pathogenesis. The standard trigger avoidance strategies are ineffective, and episodes are unpredictable. Therefore, prompt recognition and treatment as well as prophylaxis are critical. The patients should always carry an epinephrine autoinjector.

Idiopathic anaphylaxis yardstick: Practical recommendations for clinical practice

Anaphylaxis is considered idiopathic when there is no known trigger. The signs and symptoms of idiopathic anaphylaxis (IA) are identical to those of anaphylaxis because of a known cause and can include cutaneous, circulatory, respiratory, gastrointestinal, and neurologic symptoms. Idiopathic anaphylaxis can be a frustrating disease for patients and health care providers. Episodes are unpredictable, and differential diagnosis is challenging. Current anaphylaxis guidelines have little specific guidance regarding differential diagnosis and long-term management of IA. Therefore, the objective of the Idiopathic Anaphylaxis Yardstick is to use published data and the authors' combined clinical experience to provide practical recommendations for the diagnosis and management of patients with IA.

Idiopathic anaphylaxis

Idiopathic anaphylaxis (IA) or spontaneous anaphylaxis is a diagnosis of exclusion when no cause can be identified. The exact incidence and prevalence of IA are not known. The clinical manifestations of IA are similar to other known causes of anaphylaxis. A typical attack is usually acute in onset and can worsen over minutes to a few hours. The pathophysiology of IA has not yet been fully elucidated, although an IgE-mediated pathway by hitherto unidentified trigger/s might be the main underlying mechanism. Elevated concentrations of urinary histamine and its metabolite, methylimidazole acetic acid, plasma histamine and serum tryptase have been reported, consistent with mast cell activation. There is some evidence that corticosteroids reduce the frequency and severity of episodes of IA, consistent with a steroid-responsive condition. Important differential diagnoses of IA include galactose alpha-1,3 galactose (a carbohydrate contained in red meat) allergy, pigeon tick bite (Argax reflexus), wheat-dependent exercise-induced anaphylaxis, Anisakis simplex allergy and mast cell disorders. Other differential diagnoses include "allergy-mimics" such as asthma masquerading as anaphylaxis, undifferentiated somatoform disorder, panic attacks, globus hystericus, vocal cord dysfunction, scombroid poisoning, vasoactive amine intolerance, carcinoid syndrome and phaeochromocytoma. Acute treatment of IA is the same as for other forms of anaphylaxis. Long-term management is individualized and dictated by frequency and severity of symptoms and involves treatment with H1 and H2 receptor blockers, leukotriene receptor antagonist and consideration for prolonged reducing courses of oral corticosteroids. Patients should possess an epinephrine autoinjector with an anaphylaxis self-management plan. There are anecdotal reports regarding the use of omalizumab. For reasons that remain unclear, the prognosis of IA is generally favourable with appropriate treatment and patient education. If remission cannot be achieved, the diagnosis should be reconsidered.

Mastocytosis: the puzzling clinical spectrum and challenging diagnostic aspects of an enigmatic disease

Mastocytosis is a complex disorder characterized by the accumulation of abnormal mast cells (MC) in the skin, bone marrow and/or other visceral organs. The clinical manifestations result from MC-derived mediators and, less frequently, from destructive infiltration of MCs. Patients suffer from a variety of symptoms including pruritus, flushing and life-threatening anaphylaxis. Whilst mastocytosis is likely to be suspected in a patient with typical skin lesions [i.e. urticaria pigmentosa (UP)], the absence of cutaneous signs does not rule out the diagnosis of this disease. Mastocytosis should be suspected in cases of recurrent, unexplained or severe insect-induced anaphylaxis or symptoms of MC degranulation without true allergy. In rare cases, unexplained osteoporosis or unexplained haematological abnormalities can be underlying feature of mastocytosis, particularly when these conditions are associated with elevated baseline serum tryptase levels. The diagnosis is based on the World Health Organization criteria, in which the tryptase level, histopathological and immunophenotypic evaluation of MCs and molecular analysis are crucial. A somatic KIT mutation, the most common of which is D816V, is usually detectable in MCs and their progenitors. Once a diagnosis of systemic mastocytosis (SM) is made, it is mandatory to assess the burden of the disease, its activity, subtype and prognosis, and the appropriate therapy. Mastocytosis comprises seven different categories that range from indolent forms, such as cutaneous and indolent SM, to progressive forms, such as aggressive SM and MC leukaemia. Although prognosis is good in patients with indolent forms of the disease, patients with advanced categories have a poor prognosis.

The presence of mast cell clonality in patients with unexplained anaphylaxis

BACKGROUND

The mechanisms by which mast cells in patients with unexplained anaphylaxis (UEA) are triggered remain elusive. Onset of episodes is unpredictable and often recurrent. The substantial overlap between the clinical manifestations of UEA and clonal mast cell disorders (CMD) suggests an association between these rare disorders. The two forms of CMD characterized to date are systemic mastocytosis (SM) and monoclonal mast cell activation syndrome (MMAS).

OBJECTIVE

To examine the hypothesis that the pathogenesis of UEA reflects the presence of aberrant subpopulations of mast cells.

METHODS

Thirty (14 men, 16 women) patients (≥ 18 years) suffering from UEA and with no signs of cutaneous mastocytosis were recruited. Patients underwent an initial complete allergy work-up to confirm the diagnosis of UEA. Level of baseline serum tryptase (sBT) and total IgE were determined. In addition, a bone marrow examination was performed on all 30 patients to investigate possible underlying CMD.

RESULTS

Fourteen (47%) of our cases (nine men, five women) were diagnosed with CMD: 10 with SM and four with MMAS. Four of the 10 patients with SM had mast cell aggregates in their bone marrow. All patients with SM exhibited a sBT level > 11.4 ng/mL, whereas this level was elevated in only two of those with MMAS and four with UAE but not diagnosed with CMD. Total IgE levels were lower in the group of patients with CMD (P < 0.03).

CONCLUSION AND CLINICAL RELEVANCE

The pathogenic mechanism underlying UEA could be explained by the presence of immunophenotypically aberrant mast cells with clonal markers in 47% of our subjects, indicating that clonal mast cell disorders are present in a substantial subset of these patients. Thus, the presence of CMD should be considered in patients with UEA if they have an elevated level of sBT (≥ 11.4 ng/mL) and cardiovascular symptoms such as syncope.

Mediators released during human anaphylaxis

A range of mediators are generated during anaphylaxis, with redundancy of effects, multiple overlapping pathways, and involvement of several cell types. Key steps in the reaction occur at the site of initial contact, and mediators may not be detectable systemically. Furthermore, the potencies of various mediators vary enormously, and clinical effects may occur below our level of detection. We also do not know what converts (amplifies) a local reaction into systemic anaphylaxis. Murine models have identified several novel mediators that may propagate and/or regulate this process and also indicate that circulating neutrophils may play an important role in reaction amplification. Differential expression of various genes within specific intracellular signalling pathways of mediator release may further explain the varying severities of anaphylactic reactions. As our knowledge of the mechanisms of activation, key mediators, and the regulation of mediator release improves, new treatments for prevention and acute management may emerge.

The diagnosis and management of anaphylaxis practice parameter: 2010 update

These parameters were developed by the Joint Task Force on Practice Parameters, representing the American Academy of Allergy, Asthma & Immunology (AAAAI); the American College of Allergy, Asthma & Immunology (ACAAI); and the Joint Council of Allergy, Asthma and Immunology. The AAAAI and the ACAAI have jointly accepted responsibility for establishing "The Diagnosis and Management of Anaphylaxis Practice Parameter: 2010 Update." This is a complete and comprehensive document at the current time. The medical environment is a changing environment, and not all recommendations will be appropriate for all patients. Because this document incorporated the efforts of many participants, no single individual, including those who served on the Joint Task Force, is authorized to provide an official AAAAI or ACAAI interpretation of these practice parameters. Any request for information about or an interpretation of these practice parameters by the AAAAI or ACAAI should be directed to the Executive Offices of the AAAAI, the ACAAI, or the Joint Council of Allergy, Asthma and Immunology. These parameters are not designed for use by pharmaceutical companies in drug promotion.

Immunomodulatory approaches to the management of chronic urticaria: an immune-mediated inflammatory disease

Although commonly encountered in clinical practice, chronic urticaria (CU) remains difficult to treat. In contrast to acute urticaria, neither exogenous triggers nor specific immunoglobulin E are identified in most chronic cases. A body of evidence suggests that CU is represented within the spectrum of immune-mediated inflammatory diseases (IMID). Our understanding of the CU disease pathogenesis now recognizes a role for T cells, B cells, and autoantibodies, and intrinsic abnormalities of histamine-releasing effector cells, thus providing new targets of intervention beyond the current mainstay of often inadequate symptomatic treatment directed against histamine receptors and steroids, with their attendant morbidities. Agents previously used to treat other autoimmune and inflammatory diseases have demonstrated efficacy in CU. Newer biologic and nonbiologic immunomodulatory agents approved for other indications and in clinical development provide potential options for this often severe disease.

Anaphylaxis in the elderly

Anaphylaxis is a potentially fatal generalized hypersensitivity reaction leading to multiorgan dysfunction. It involves multiple mediators using several different pathways for the development of a systemic response. The elderly differ from other age groups in terms of the risk factors, causative agents and the development of compensatory mechanisms. The presence of comorbidities and polypharmacy has a marked influence on treatment and outcome in the elderly. This article aims at a general understanding of anaphylaxis with special reference to the elderly.

Idiopathic Anaphylaxis

Idiopathic anaphylaxis is a prednisone-responsive condition without external cause, but it can coexist with food-, medication-, or exercise-induced anaphylaxis. Mast cell activation may occur at night or after foods that have been eaten with impunity many times previously. Idiopathic anaphylaxis can be classified into frequent (if there are six or more episodes per year or two episodes in the last 2 months) or infrequent (if episodes occur less often). Idiopathic anaphylaxis-generalized consists of urticaria or angioedema associated with severe respiratory distress, syncope or hypotension, and gastrointestinal symptoms. Idiopathic anaphylaxis-angioedema consists of massive tongue enlargement or severe pharyngeal or laryngeal swelling with urticaria or peripheral angioedema. The differential diagnosis of idiopathic anaphylaxis is reviewed, and treatment approaches are presented.

Anaphylaxis, killer allergy: long-term management in the community

Traditionally, physicians are trained to diagnose and treat anaphylaxis as an acute emergency in a health care setting. In addition to this crucial and time-honored role, we should be cognizant of our wider responsibility to (1) provide a risk assessment for individuals with anaphylaxis, (2) prevent future anaphylaxis episodes by developing long-term personalized risk reduction strategies for affected individuals, and (3) emphasize anaphylaxis education. Risk assessment should include verification of the trigger factor or factors for the anaphylaxis episode by obtaining a comprehensive history and performing relevant investigations, including allergen skin tests and measurement of allergen-specific IgE in serum. In addition, the potential effect of comorbidities and concurrently administered medications on the recognition and emergency treatment of subsequent episodes should be determined. Risk reduction strategies should be personalized to include information about avoidance of specific triggers and initiation of relevant specific preventive treatment (eg, venom immunotherapy). At-risk individuals should be coached in the use of self-injectable epinephrine and equipped with an anaphylaxis emergency action plan and with accurate medical identification. Anaphylaxis education should be provided for these individuals, their families and caregivers, health care professionals, and the general public. Further development of an optimal diagnostic test for anaphylaxis and of tests and algorithms to predict future risk and prevent fatality are urgently needed.

Life-threatening severe allergic reactions: urticaria, angioedema, and anaphylaxis

Urticaria, angioedema and anaphylaxis are life threatening skin diseases. Allergological emergencies are common; drugs, food, food ingredients/additives, insects, and many other factors have been reported to elicit anaphylactic reactions. The severity of symptoms ranges from pruritus to generalized skin eruptions, gastrointestinal, bronchial problems to systemic anaphylaxis and cardiovascular emergencies. The pathomechanisms and treatment of urticarias, angioedema and anaphylaxis are described. In some situations emergency kit: antihistamines, steroids, betamimetics and adrenaline is needed. Familiarity with the early diagnosis and correct management should be acknowledegable for dermatologists to recognize these allergic reactions and must be prepared to administer emergency kit.

A current review of idiopathic anaphylaxis

PURPOSE OF REVIEW

Idiopathic anaphylaxis is a well established entity that can lead to unnecessary morbidity and costs if not diagnosed and managed properly. To ensure that more patients benefit from proper care, the medical community needs to be better informed of this rare disease.

RECENT FINDINGS

The classification and treatment of idiopathic anaphylaxis have been fine-tuned over the past 25 years without knowledge of the disease's underlying mechanism, despite much research dedicated towards this end. The observation that idiopathic anaphylaxis is a steroid-responsive disease has led to a more recent view that its underlying mechanism may be autoimmune in nature.

SUMMARY

Although the underlying pathogenesis of idiopathic anaphylaxis remains unknown, thousands of patients in the United States have been successfully treated with the currently recommended regimen of steroids and antihistamines. If diagnosed and treated properly, approximately 85% of patients will have a sustained remission after being tapered off corticosteroids.