MCQ#01
Correct Answer is D
Explanation:
The majority of urticaria and angioedema are mast cell mediated conditions resulting in the release of histamine, leukotrienes, and other mast cell mediators into the superficial dermis (urticaria) and deep dermis (angioedema). In children, common viral or bacterial infections account for 80% of acute urticaria. Treatment of acute urticaria and angioedema should focus on identifying and discontinuing any underlying triggering process and symptom suppression until resolution of the acute episode.
Symptom suppression can often be achieved with administration of H1 antihistamine receptor antagonists. It is most efficient to maximize the H1-receptor antagonist therapy prior to adding additional medications. The use of first generation H1-receptor antagonists, such as diphenhydramine, is limited by their sedating and anticholinergic side effects.
Cetirizine, a second-generation H1-receptor antagonist, is preferable for controlling urticarial symptoms that persist for more than a few days.
H2-receptor antagonists (ranitidine) and leukotriene inhibitors (montelukast) are useful adjunctive medications.
Short courses of oral steroids (prednisone) can be used to control severe urticaria that is refractory to high dose antihistamines, but should not be prior to a trial of antihistamine therapy.
MCQ#02
Correct Answer is C
Explanation:
Food allergies have a strong genetic component. Siblings of a peanut allergic child are 6 times more likely to develop a peanut allergy. 64% of monozygotic twins share a peanut allergy compared to 3% of dizygotic twins.
MCQ#03
Correct Answer is D
Explanation:
Food allergies can be grouped into 2 general categories: IgE mediated and non-IgE-mediated. IgE-mediated reactions are typically of rapid onset with clinical symptoms usually developing within minutes to a few hours of ingestion of the offending food. These reactions are due to release of mast cell granules and present with the typical characteristics of type I hypersensitivity reactions (flushing, urticaria, and/or angioedema).
The diagnostic workup for a suspected IgE-medicated food allergy includes a skin prick test and/or measurement of serum food-specific IgE antibodies. Both of these tests have sensitivity estimated to be >85%. Specificity, however, is <40%, since both tests measure allergic sensitization and may not correlate with clinical allergy. Clinical allergy can only be assessed by an oral food challenge. For some common food allergens, studies have suggested cut-off values for serum food-specific IgE antibodies that can predict the likelihood of developing systemic allergic reactions in a particular patient.
Intradermal skin testing requires a small amount of the allergen solution is injected into the skin. An intradermal skin test may be done when a substance does not cause a reaction in the skin prick test, but is still a suspected allergen for a given patient. The intradermal test is more sensitive than the skin prick test, but also has more false-positive results. It is not used
for the diagnosis of IgE-mediated food allergy, but rather for the evaluation of seasonal and perennial AR.
The atopy patch test is used to elicit cellular mediated hypersensitivity reactions in sensitized subjects. Patient skin is exposed to the allergen usually for 48 hours and reactions are usually interpreted at 72 hours. Patch testing is used for the assessment of contact allergen sensitization, but is only recently being evaluated for cellular-mediated food hypersensitivity disorders. While patch testing has shown promise for the diagnosis of non-IgE mediated food allergy, there are currently no standardized reagents, application methods, or guidelines for interpretation.
MCQ#04
Correct Answer is A
Explanation:
Current management of food allergies relies on the careful elimination of the offending food from the diet, including instruction on reading of labels and often requires education of the parents by a dietician. Institution of therapeutic measures to stall the development of severe reactions in the case of an accidental food exposure is also necessary. All patients with a history of a systemic reaction to food should be prescribed injectable epinephrine and instructed on its use. The drug should be employed quickly in the case of an impending anaphylactic reaction. Daily use, however, is not indicated.
Milder food allergic reactions, those involving the skin or the gastrointestinal system exclusively, can be treated with oral antihistamines. Oral antihistamines should be used for
symptoms only and daily use is not indicated.
The indication of glucocorticoids for the treatment of acute food allergic reactions is controversial. There is no consistent evidence that glucocorticoids prevent the development of late-phase reactions and are not routinely indicated.
The use of oral immunotherapy for desensitization to food allergens is currently an area of investigation. The safety and efficacy of this approach has not been established in infants
and children.
MCQ#05
Correct Answer is E
Explanation:
Drug reactions can be classified into immunologic and nonimmunologic etiologies. The majority (75–80%) of adverse drug reactions are predictable, nonimmunologic effects, including: reactions due to overdose, toxicity, pharmacologic side effects, indirect side effects, and drug-drug interactions. The remaining 20–25% of adverse drug events are due to unpredictable effects, which may or may not be immune-mediated.Immune-mediated reactions constituting true drug hypersensitivity account for 5–10% of all drug reactions.
Drug hypersensitivity reactions commonly manifest with dermatologic symptoms. Typically an erythematous, maculopapular rash develops within 2 weeks of drug initiation, originating on the trunk with eventual spread to the limbs.
Pruritis and low-grade fever may accompany the drug eruption. Nephrotoxicity and ototoxicity are known dose-dependent side of effects of vancomycin and gentamicin respectively. Nausea and vomiting is a common adverse drug reaction to certain antibiotics, but nausea and vomiting do not represent an immunologic drug reaction.
Infectious mononucleosis is most commonly secondary to infection with the Epstein–Barr virus. A rash is a relatively common adverse effect of amoxicillin treatment in patients with acute Epstein–Barr virus. It is a non-immunologically mediated reaction. Amoxicillin is not indicated for the treatment of viral infections including the Epstein–Barr virus.
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