CLINICAL ENCOUNTERS
PSORIASIS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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allergic contact dermatitis
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irritant contact dermatitis
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lichen simplex chronicus
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None of the above
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Detailed explanation-1: -Delayed-type hypersensitivity (DTH) is defined as the recruitment of T cells into tissues to be activated by antigen-presenting cells to produce cytokines that mediate local inflammation. CD8+ T cells are now known to mediate DTH responses in allergic contact dermatitis, drug eruptions, asthma, and autoimmune diseases.
Detailed explanation-2: -They are also termed type IV hypersensitivity reactions. Delayed hypersensitivity is a major mechanism of defense against various intracellular pathogens, including mycobacteria, fungi, and certain parasites, and it occurs in transplant rejection and tumor immunity.
Detailed explanation-3: -Allergic contact dermatitis is a type 4 or delayed hypersensitivity reaction and occurs 48–72 hours after exposure to the allergen. The mechanism involves CD4+ T-lymphocytes, which recognise an antigen on the skin surface, releasing cytokines that activate the immune system and cause the dermatitis.