Question
A 45-year-old farmer has itchy erythematous papular lesions on face, neck, ‘V’ area of chest, dorsum of hands and forearms for 3 years. The lesions are more severe in summers and improve by 75% in winters. The most appropriate test to diagnose the condition would be:
| A. |
Skin biopsy
|
| B. |
Estimation of IgE levels in blood
|
| C. |
Patch test
|
| D. |
Intradermal prick test
|
Show Answer
|
Correct Answer » C
Explanation
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|
The clinical picture suggests: Chronic actinic dermatitis / airborne contact dermatitis
Supporting features:
- Farmer (exposure to plants/pollens/agrochemicals)
- Chronic itchy papular erythematous lesions
- Involvement of sun-exposed areas:
- Face
- Neck
- V area of chest
- Dorsum of hands and forearms
- Worse in summers
- Improves in winters
Best diagnostic test:
Patch test
- Detects delayed type (Type IV) hypersensitivity
- Helps identify contact allergens responsible for airborne contact dermatitis
Why Other Options are Incorrect
A. Skin biopsy
- Histopathology is nonspecific
- Cannot reliably identify allergen/contact sensitivity
B. Estimation of IgE levels in blood
- Elevated in atopy and Type I hypersensitivity
- Not useful for diagnosing contact dermatitis
D. Intradermal prick test
- Used for immediate (Type I) hypersensitivity reactions
- Useful in:
- Urticaria
- Allergic rhinitis
- Food allergy
- Not useful for delayed hypersensitivity/contact dermatitis
