This specific allergy is related to a carbohydrate called alpha-gal found in red meat. So do patients become allergic to themselves? No! Interestingly, the alpha-gal molecule is found in all mammals except apes, humans, and Old World monkeys.
Anaphylaxis: involvement of respiratory (respiratory compromiseb) and/or circulatory system (vasodilatory shock)
Additionally, drugs which have the suffix “ide” (e.g., chlorpropamide —antidiabetic drug, diuretics—furosemide, acetazolamide, hydrochlorothiazide, bumetanide) have some sulfa component, but most are well tolerated and have very low cross-reactivity with other sulfonamides.
These drugs can cause all four types of hypersensitivity (urticaria, anaphylaxis, autoimmune hemolytic anemia, serum sickness, allergic interstitial nephritis, maculopapular rash, toxic epidermal necrolysis, Stevens-Johnson syndrome, etc.). They will be called “highly allergenic drugs” for the purpose of this book.
1. With diagnosis of otitis media, patient was started on amoxicillin more than a week ago. Patient now presents with new onset fever, rash, joint pain, and lymphadenopathy. ANA is negative. What is the likely dx?
An adult patient has hypotension and shortness of breath after a bee sting. Patient reports no hx of bee sting in the past. Exam reveals diffuse swelling of eyelids, lips, and bilateral extensive wheezing. He then develops hypotension.
Physical urticariaa, or underlying systemic disorder (autoimmune, vasculitis, malignancy, etc.)
Antihistamines (H1– blockers)b
In severe cases not responding to above regimen, use omalizumab (anti-IgE antibody). If not responding, use anti-inflammatory agents such as dapsone, sulfasalazine, hydroxychloroquine, or in more severe cases, immunosuppressives such as tacrolimus.
Respiratory distress and arresta
Etiology: Most commonly due to allergic triggers such as foods (e.g., peanuts, shellfish, eggs), pollen, medications (highly allergenic drugs), insect bites, rubber latex, contrast media, etc. This can also be due to physical factors such as exercise, sunlight, hot or cold temperatures, etc.
1. Bradykinin-mediated angioedema due to ACE-i: this is the most common form of bradykinin-mediated angioedema (it can occur any time after initiation)b
Pathophysiology: Decreased activity of Cl inhibitor → increased C1 activity→increased activation and consumption of complement proteins (low C3, C4) →increased production of bradykinin and other edema mediators.
aAfter an anaphylaxis episode, the serum tryptase level increases (tryptase is a unique mast cell protein). This is useful for diagnosis in atypical cases, but the level needs to be drawn within few hours of symptom onset, as it rapidly falls to normal levels within few hours of the episode.
b Angiotensin-receptor blockers (ARBs), unlike ACE-i, do not decrease bradykinin metabolism. They act only by blocking angiotensin receptors. Hence ARBs can be given to patient with ACE-i-related angioedema.
dFor example, patient has anaphylaxis due to bee sting, but he is a bee farmer and would like to continue to work. Prior to desensitization any adrenergic blocking agents (such as B-blockers) must be stopped, because epinephrine might be required if the patient develops an anaphylactic reaction during the procedure.