Idiopathic Anaphylaxis
Section snippets
Definitions
As stated, anaphylaxis implies a potential for death, although most episodes of anaphylaxis are not fatal. Simons [10] has suggested that anaphylaxis be considered as either immunologic (IgE or Fcε RI mediated), nonimmunologic, or idiopathic. The National Institute of Allergy and Infectious Diseases/Food Allergy and Anaphylaxis Network defines anaphylaxis as “a severe, potentially fatal, systemic allergic reaction that occurs suddenly after contact with an allergy-causing substance” [11]. The
Classification of anaphylactic episodes
Idiopathic anaphylaxis has been classified into two categories [3], [13]. Idiopathic anaphylaxis—generalized (IA-G) is present when there is a sudden episode that includes urticaria or angioedema associated with acute bronchoconstriction, voice change or stridor, syncope or proven hypotension, with or without abdominal pain and diarrhea [3]. Alternatively, idiopathic anaphylaxis—angioedema (IA-A) refers to anaphylaxis that is characterized by marked upper airway obstruction attributable to
Incidence of idiopathic anaphylaxis
In 1995, the prevalence of idiopathic anaphylaxis in the United States was estimated to be 33,000 cases [16]. In series of patients being assessed in emergency departments for anaphylaxis, the incidence of idiopathic anaphylaxis may be estimated by subtracting the number of cases in which identifiable causes are listed from the total number of visits. For example, 6 of 97 (6.1%) patients in New York City had “unclear or undetermined” causes [17] compared with as many as 38 of 142 (27%) patients
Nearly fatal and fatal idiopathic anaphylaxis
There are three reported fatalities from idiopathic anaphylaxis [24], [25]. One 43-year-old patient who had asthma had a 12-year history of anaphylaxis with apparently more than 100 emergency department visits over that time period [24]. The patient's episodes often consisted of acute onset of dyspnea and abdominal pain that were associated at times with fecal incontinence and loss of consciousness [24]. The patient would self-inject epinephrine every 1 to 2 months [24]. His food skin tests
Pathogenesis of idiopathic anaphylaxis
Mast cell activation associated with anaphylactic reactions has been supported by detection of urinary histamine [5], [6], urinary methylimidazole acetic acid [7], plasma histamine [8], and serum tryptase [7], [9] In the absence of acute anaphylaxis, there should be normal values. A patient who had anaphylaxis for 10 years, considered to be idiopathic, had an elevated serum β tryptase concentration of 110 ng/mL (normal <1 ng/mL) 26 hours after the onset of an episode, at which time a few
Clinical presentation and demographics of idiopathic anaphylaxis
From a series of 335 patients, all had experienced either urticaria or angioedema [3]. Upper airway obstruction occurred in 210 (63%) and acute bronchoconstriction was reported in 132 (39%) [3]. Hypotension or syncope was present in 78 (23%) and gastrointestinal symptoms were described in 75 (22%) [3]. Urticaria or angioedema that was pre-existing had occurred in 78 (23%) and exercise-induced anaphylaxis was diagnosed in 38 (11%) [3]. Forty eight percent of patients were atopic, which included
Classification of idiopathic anaphylaxis
Idiopathic anaphylaxis has been classified based on whether there is a generalized reaction (IA-G) with hypotension, syncope, or severe bronchoconstriction, or if upper airway obstruction is prominent (IA-A) for angioedema of the tongue, pharynx, or larynx [13]. If episodes are occurring twice in 2 months or six or more per year, then the designation frequent is added (IA-G-F or IA-A-F) [13]. Alternatively, if episodes are less frequent, then the designation is (IA-G-I or IA-A-I) for infrequent
Differential diagnosis of idiopathic anaphylaxis
The differential diagnosis of idiopathic anaphylaxis includes organic and nonorganic conditions [41], [43]. A summary of these causes is presented in Box 1. The list is not all-inclusive of causes of anaphylaxis. The diagnosis of idiopathic anaphylaxis is one of exclusion of other causes with reasonable certainty. Some areas for consideration are presented in this section.
Acute management
At the onset of urticaria, abdominal pain, generalized pruritus, or other symptoms consistent with anaphylaxis, patients should self-inject epinephrine 0.3 mg intramuscularly and take prednisone 50 mg and an H1 antagonist, such as cetirizine 10 mg. Other H1 antagonists are acceptable. The patient should contact a physician for advice, call 911, or go to an emergency department depending on the circumstances of the case. Additional intensive therapy may be needed in the emergency department.
Summary
Idiopathic anaphylaxis is a diagnosis of reasonable exclusion in which referral to an allergist-immunologist is advisable. For frequent episodes, it is recommended that a 3-month empiric course of prednisone and H1 antagonist, with or without albuterol, be used to reduce the number and severity of episodes. For infrequent episodes, expectant management with the triple therapy of epinephrine, prednisone, and H1 antagonist be used. Some patients who have idiopathic anaphylaxis can be expected to
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2015, Immunology and Allergy Clinics of North AmericaCitation Excerpt :However, after puberty and until menarche, the incidence has been reported to be similar in men and women.6 The classification of IA is based on frequency of episodes and clinical manifestations.7 Frequent episodes are defined as having at least 2 episodes in the preceding 2 months or at least 6 episodes in the preceding year.
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2014, Journal of Allergy and Clinical Immunology: In PracticeCitation Excerpt :However, urticaria and angioedema are not characteristic of the acute episodes of these conditions. Once it was learned that patients with frequent episodes of anaphylaxis of unknown cause would experience a reduced incidence and severity of episodes when treated empirically with prednisone, hydroxyzine, and, if tolerated, oral albuterol, this combination of drugs has been used as a diagnostic and therapeutic regimen.7,27,72 In particular, if the episodes of anaphylaxis continued despite the first 2 weeks of a minimum dose of prednisone 40 mg daily, in nearly all cases, idiopathic anaphylaxis can be excluded.46
Supported by the Ernest S. Bazley Grant to Northwestern Memorial Hospital and Northwestern University.