Which of the following is an accurate description of a type-1 hypersensitivity reaction?

A. Most type-1 reactions are allergic: This statement is accurate. Type-1 hypersensitivity reactions are typically associated with allergies. When a person is exposed to a specific allergen (like pollen or certain foods), their immune system overreacts, leading to various symptoms, from mild to severe.

B. It is mediated by IgA: This statement is incorrect. Type-1 hypersensitivity reactions are primarily mediated by immunoglobulin E (IgE) antibodies. When these antibodies bind to allergens, they trigger the release of histamine and other chemicals, causing allergic symptoms.

C. It never contributes to autoimmune diseases: This statement is incorrect. While type-1 hypersensitivity reactions are often associated with allergies, they are distinct from autoimmune diseases. In autoimmune diseases, the immune system mistakenly attacks the body's own cells and tissues, which is a different mechanism from hypersensitivity reactions.

D. Most occur against medications: This statement is not entirely accurate. While some type-1 hypersensitivity reactions can be triggered by medications (like penicillin), they can also be caused by various other allergens such as pollen, animal dander, insect venom, and certain foods. The prevalence of medication-induced type-1 reactions varies, and it's not accurate to say that most occur against medications.

A. Hypertension: Anaphylaxis often leads to a rapid drop in blood pressure (hypotension) rather than hypertension. Hypotension is a more common symptom because of the severe vasodilation that occurs during anaphylactic reactions.

B. Angioedema: Yes, angioedema is a common clinical manifestation of anaphylaxis. Angioedema involves swelling of the deeper layers of the skin, often around the eyes and lips. It can also affect the throat, which can be life-threatening due to airway obstruction.

C. Petechiae: Petechiae are small red or purple spots that appear on the skin and are caused by bleeding into the skin's tissues. They are not a typical manifestation of anaphylaxis.

D. Bronchospasm: Yes, bronchospasm is a hallmark clinical manifestation of anaphylaxis. It involves the sudden constriction of the airways, leading to difficulty in breathing and wheezing.