Triage: Itchy rash for weeks, antifungal cream not helping
History of Present Illness: A man in his mid 40’s presents to the hospital with 2 months of rash in his lower abdomen. He is worried it could be herpes due to the location and his dating habits
Vital signs: normal
Physical Exam: normal except as below
What is the most likely diagnosis?
- A) Tinea versicolor
- B) Herpes simplex
- C) Contact dermatitis
- D) None of the above
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- Emergency Medicine 1-Minute Consult, 5th edition
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ANSWER: What is the most likely diagnosis?
- A) Tinea versicolor
- B) Herpes simplex
- C) Contact dermatitis – CORRECT – See below
- D) None of the above
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CASE OUTCOME: He had a newish belt and often wore pants and a belt without a shirt. The belt buckle was large and made from nickel. He was diagnosed with contact dermatitis (type 4 hypersensitivity reaction).
ACID mnemonic for the 4 types of Hypersensitivity reactions
- Allergic = Type I: reaction mediated by IgE antibodies. Examples: bee sting, hives, anaphylaxis
- Cytotoxic = Type II: cytotoxic reaction mediated by IgG or IgM antibodies. Examples: Hemolysis, graft rejection
- Immune Complex = Type III: reaction mediated by immune complexes. Examples: Serum sickness, lupus
- Delayed = Type IV: delayed reaction mediated by cellular response. Examples: PPD, nickel, poison oak, vaccines