Page 629 - Clinical Immunology_ Principles and Practice ( PDFDrive )

CHaPtEr 43 Allergic Reactions to Stinging and Biting Insects 605

and flare reaction, followed by a swelling of up to 5–10 cm in mechanisms are likely involved. The causal relation to the sting
diameter. Usually, local symptoms resolve within a few hours. event often remains uncertain. Serum sickness–like syndromes
The fire ant (S. invicta) attaches to the skin by means of its with fever, arthralgias, exanthema, and lymphadenopathy are
powerful mandibles and then stings, releasing venom that well documented. Less frequently reported complications of
produces a characteristic firelike pain. If not removed, it will Hymenoptera stings include diseases of the nervous system
continue to rotate in a pivotal fashion, repeatedly injecting further (peripheral neuropathy, polyradiculomyelitis, extrapyramidal
10
small amounts of venom. After the ant stings, a vesicle is left syndromes, acute disseminated encephalomyelitis), kidneys
behind, which later develops into a pustule that only heals after (glomerulonephritis, interstitial nephritis), or blood and blood
1–2 weeks. 3 vessels (hemolytic anemia, thrombocytopenia, Henoch-Schönlein
syndrome and other forms of vasculitis). In these situations, a
Large Local Reactions causal relation to the sting is less well documented.
Large local reactions (LLRs) are defined as swellings around the
sting site exceeding 10 cm in diameter, developing minutes to EPIDEMIOLOGICAL ASPECTS
1
hours after the sting and lasting more than 24 hours. LLRs may
cause significant discomfort, especially when they last for days Prevalence of Allergy to Stings by Flying Hymenoptera
or even weeks and involve a whole limb, eyelids, or lips. Sometimes
they are accompanied by lymphadenopathy or lymphangitis. KEY CONCEPtS
They may also be associated with nonspecific systemic inflam-
matory symptoms, such as malaise, fever, shivering, or headache. • Awareness of the most relevant insects, specifically Hymenoptera
and their entomological subdivisions, causing immunoglobulin E
However, the development of local infection, abscesses, or a (IgE)–mediated allergies
phlegmon at the sting site is inhibited by the bacteriostatic effect • Assessment of clinical symptoms and classification of Hymenoptera
of Hymenoptera venoms. In contrast, scratching after stings by venom allergy
the American fire ant or bites from blood-sucking insects, such • Evaluation of persons and circumstances at risk for Hymenoptera
as midges, can lead to skin infection. venom allergy
The pathogenesis of LLRs is thought to be based on IgE- • Knowledge of appropriate diagnosis of Hymenoptera venom allergy,
mediated and/or cell-mediated immune mechanisms, most likely potential diagnostic and therapeutic control test tools
a combination of both. 1,2
Cumulative lifetime sting rates of 61–95% have been reported
Systemic Reactions in people aged 16–65 years. Of course, this can vary considerably
Systemic reactions (SRs), including anaphylactic reactions, are in different regions of the world. Asymptomatic sensitization
usually mediated by IgE (Chapter 42). Affected organs include with the development of specific IgE to bee and wasp venoms
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skin (pruritus, urticaria, flush, angioedema), the gastrointestinal is a frequent finding and has been reported in up to 40%.
(GI) tract (cramps, vomiting or diarrhea, dysphagia), the respira- Hymenoptera sting allergy can occur at any age. In general,
tory tract (laryngeal edema, bronchial obstruction, pulmonary because of their higher level of outdoor activities, men are more
edema), and the cardiovascular system (arterial hypotension, frequently stung compared with women, and children more often
shock, arrhythmias, loss of consciousness with incontinence). compared with adults. 14
The most commonly used classification of SRs was developed The reported cumulative lifetime prevalence of LLRs ranges
11
2
by Müeller. Symptoms appear most often within a few minutes from 2% to 26%, that of SRs from 0.3% to 5%. Among beekeep-
15
to 1 hour after the sting. The patient recovers usually within a ers, it varies between 14% and 43%. LLRs are not predictive
13
few hours. A protracted course over more than a day or a biphasic for SRs in the event of a subsequent Hymenoptera sting. In
course has been described but is rare. Europe and the United States, SRs are more frequently caused
Lasting morbidity, for example, myocardial or cerebrovascular by vespids than by honeybees. In the southern states of the United
infarction, as a consequence of SRs or even fatal reactions can States and in Australia, ants are important causes of SR.
occur, but these are rare (see “Epidemiological aspects”).
Risk Factors for Hymenoptera Allergy
Systemic Toxic Reactions The risk of developing a sting allergy increases with the number
Toxic reactions are dose dependent, and a clinically significant of stings, especially if two stings occur within a short period (up
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toxic effect only needs to be considered after multiple stings— to 2 months). However, beekeepers stung less than 10 times a
1,2
usually 50 to several hundred. The main toxic effects develop year have a much higher risk for SRs compared with those stung
15
within hours to days and comprise rhabdomyolysis and intra- more than 200 times a year. Even after successful venom
vascular hemolysis leading to acute renal failure with tubular immunotherapy, the risk of recurrent SRs after Hymenoptera
17
necrosis. Myocardial damage, hepatic dysfunction, coagulation stings persists throughout life. Cardiovascular diseases and their
disorders, and brain edema and/or necrosis may occur. The treatment with β-blocking drugs and angiotensin-converting
number of stings needed to cause a fatal reaction in adults varies enzyme (ACE) inhibitors are associated with more severe sting
between 200 and 1000. In small children, however, fewer than reactions, sometimes also with lasting morbidity caused by cardiac
50 stings may be lethal. In most cases, death is not immediate or cerebrovascular infarction as a result of anaphylaxis. 1,18,19
but occurs after several days. However, β-blockers do not increase the overall risk of systemic
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sting reactions. Systemic mastocytosis (indicated by elevated
Unusual Reactions baseline serum tryptase) is a risk factor for severe or even fatal
19
Various unusual sting reactions can occur: these are rare and systemic sting reactions. Atopy is not more frequent in patients
appear after hours to days. More than half of them follow with Hymenoptera sting allergy than in the general population.
immediate local or SRs. 1,12 Non–IgE-mediated immunological However, in patients with atopy and Hymenoptera venom allergy,