Review Question - QID 104220

This child is presenting with a delayed type IV hypersensitivity reaction likely secondary to poison ivy exposure causing a contact dermatitis. Hashimoto thyroiditis is also a type IV hypersensitivity reaction.

Poison ivy causes an allergic contact dermatitis. It is an example of a delayed type IV hypersensitivity reaction which occurs through the sensitization of T-cells. It is commonly found in the pediatric population after a history of spending time in rural and wooded areas. The characteristic erythematous, vesicular, and weeping rash is commonly found over a single area of exposure to the antigen. Treatment is achieved in most circumstances with topical corticosteroids.

Figure A is a photograph of the characteristic erythematous, vesicular, and pruritic rash that is associated with poison ivy exposure.

Incorrect Answers:
Answer 1: Anaphylaxis is a type I hypersensitivity reaction which occurs secondary to IgE. It presents with hypotension, tachycardia, wheezing, and airway swelling.

Answer 2: Goodpasture syndrome is a type II hypersensitivity reaction where antibodies are directed against the basement membrane of the lung and kidney causing the presentation of hemoptysis and hematuria.

Answer 4: Serum sickness is a type III hypersensitivity reaction which occurs secondary to deposition of immune complexes. It presents with fever, fatigue, arthralgias, and kidney injury.

Answer 5: Urticaria occurs secondary to mast cell degranulation and presents with pruritic lesions (hives) after exposure to certain antigens or medications.

Bullet Summary:
Contact dermatitis is a type IV hypersensitivity reaction which presents with pruritic vesicles.