Anaphylaxis is a rapidly progressing, multisystem hypersensitivity reaction. Systems with high concentrations of mast cells are the most affected, such as the skin, respiratory system, GI tract and cardiovascular system. Anaphylaxis can begin immediately, particularly if the trigger is not processed by the digestive system (inhaled, for example). For triggers ingested and processed in the GI system, it can take hours for a reaction to begin. Once started, it can progress rapidly to life-threatening multi-organ involvement. Airway compromise is the most common cause of death from anaphylaxis. Death can occur in 30 minutes or less.
Anaphylaxis is very uncommon in the general population, with less than 2% people experiencing it yearly. The most common causes of anaphylaxis in this group are food (33%), insect stings (3%), antisera (2%) and aspirin (0.9%). Exposure to triggers for diagnostic or treatment purposes, and occupational exposures to triggers are risk factors. Use of beta-blockers or ACE inhibitors (blood pressure medications) and heart disease can cause more severe reactions.
Sex was not found to be a risk factor. Male patients more likely to anaphylax due to insect bites, while female patients are more likely to anaphylax due to IV muscle relaxants, aspirin and latex. However, these findings are due to frequency of exposure. Atopic diseases, like eczema, allergic asthma and allergic rhinoconjunctivitis have long been cited as risk factors, but this was found to be untrue in a 2008 study. While reactions can be more severe in patients with atopic disease, they are not more frequent when compared to people without these conditions.
Sensitivity to specific triggers can be genetic. Radiology contrast agents, opiates and exercise most likely to cause anaphylaxis that is not mediated by IgE.
It is well known that people with mastocytosis are more likely to experience anaphylaxis than the general public. In adults with any type of mastocytosis, 49% experience anaphylaxis; in children with any type of mastocytosis, 9% will experience it. Patients with systemic mastocytosis were more likely to anaphylax than those with cutaneous mastocytosis. Only children with extensive skin involvement experienced anaphylaxis in this study.
In adults, 48% of the reactions were severe, with 38% causing unconsciousness. 60% were Grade III anaphylaxis. 19% were caused by bee or wasp stings; 16% by food (always histamine rich, and tested negative for corresponding IgE); 9% by medication; and 13% had no identifiable trigger. Interestingly, 26% anaphylaxed only after exposure to a combination of triggers, such as alcohol, exercise and insect bites. This is relevant because it implies that mastocytosis patients have a threshold for anaphylaxis – that if enough triggers are present, they have the propensity to anaphylax, and that it is only the amount of trigger required that varies among mastocytosis patients. Adults without skin involvement, such as urticarial pigmentosa (UP) lesions, were more likely to anaphylax.
In adult Grade III anaphylaxis, symptoms were more frequently cardiovascular in nature, with dizziness and fainting occurring 44% of the time; rapid heartbeat, 47%; low blood pressure or shock, 50%. Difficulty breathing was present 44% of the time; nausea, 36%; diarrhea, 33%; and flushing, 33%. 19.2% of patients had no rapid heartbeat, low blood pressure or difficulty breathing. Take note of this, masto kids – this study just validated for us that it is possible to anaphylax without difficulty breathing, low blood pressure or rapid heartbeat.
Only children with severe skin involvement (>45% lesions) experienced anaphylaxis in this study. Children were much more likely to have not an obvious trigger (67%). Most common known triggers were foods. Cold water caused one reaction, as did vaccination. Bee or wasp stings never caused anaphylaxis in children. Reactions involved abdominal pain, vomiting, itching, nasal congestion, and rapid heartbeat. As with adults, children with systemic disease were more likely to experience anaphylaxis than those with cutaneous disease.
Children with solitary mastocytomas were not found to anaphylax, and only one child with diffuse cutaneous mastocytosis did so. Three children with extensive, mast cell infiltrated skin lesions (>45%) also anaphylaxed. A previous study found that children with fatal anaphylaxis all had severe, blistering skin disease.
Patients who anaphylaxed were found to have higher base tryptase measurements than those who did not. However, these numbers were hugely variable. For adults who anaphylaxed, tryptase was reported as 60.2 ± 55 ng/mL, meaning that it ranged from 5.2-115.2 ng/mL. For those without anaphylaxis, tryptase measurements ranged from 0-54.2 ng/mL.
A key take-home point from this study was that patients presenting to emergency rooms with anaphylaxis were almost always treated incorrectly and not in accordance with published guidelines. Only 11% of adults were administered epinephrine, while no children were given it. Most people received antihistamines and corticosteroids. Approximately 25% were hospitalized. The appropriate treatment for Grade III anaphylaxis is epinephrine.
Bottom line: adults with mastocytosis are 25X more likely than the general public to anaphylax. Adults without skin involvement were more likely to anaphylax. Children with severe skin involvement are 5X more likely than the general public to anaphylax. No episodes of anaphylaxis in children without severe skin involvement were reported in this study. In both populations, people with systemic mastocytosis were more likely to experience anaphylaxis than those with cutaneous disease.
Sources:
http://onlinelibrary.wiley.com/doi/10.1111/j.1398-9995.2007.01569.x/full
https://www.clinicalkey.com/topics/immunology/anaphylaxis.html
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