ABD ABD Photodermatology and UV Effects 1 — Questions and Answers
Question 1: Which idiopathic photodermatosis is the most common, affecting up to 10-20% of the population in temperate climates?
- Solar urticaria
- Polymorphous light eruption (PMLE) (Correct answer)
- Chronic actinic dermatitis
- Actinic prurigo
Correct answer: Polymorphous light eruption (PMLE)
Polymorphous light eruption (PMLE) is the most common idiopathic photodermatosis, presenting with pruritic papules, plaques, or vesicles on sun-exposed skin in spring/summer.
Question 2: UVA radiation (320-400nm) primarily penetrates to which level of the skin?
- Stratum corneum only
- Epidermis only
- Dermis (Correct answer)
- Subcutaneous fat
Correct answer: Dermis
UVA radiation penetrates deeply into the dermis, reaching dermal fibroblasts and blood vessels, and is the primary driver of photoaging and tanning through oxidative mechanisms.
Question 3: How does photoallergic contact dermatitis differ from phototoxic dermatitis?
- Phototoxic reactions require prior sensitization
- Photoallergic reactions require prior sensitization and involve a Type IV immune response (Correct answer)
- Phototoxic reactions can spread beyond sun-exposed areas
- Photoallergic reactions always cause blistering on first exposure
Correct answer: Photoallergic reactions require prior sensitization and involve a Type IV immune response
Photoallergic reactions require prior sensitization, involve a Type IV delayed hypersensitivity immune response, and can spread beyond directly sun-exposed sites.
Question 4: Hydroa vacciniforme is associated with latent infection with which virus?
- Human herpesvirus 6 (HHV-6)
- Epstein-Barr virus (EBV) (Correct answer)
- Cytomegalovirus (CMV)
- Herpes simplex virus type 1
Correct answer: Epstein-Barr virus (EBV)
Hydroa vacciniforme and hydroa vacciniforme-like lymphoproliferative disorder are strongly associated with Epstein-Barr virus (EBV) infection.
Question 5: The Fitzpatrick skin phototype classification system categorizes human skin into how many phototypes?
- 4
- 5
- 6 (Correct answer)
- 8
Correct answer: 6
The Fitzpatrick scale classifies skin into 6 phototypes (I-VI) based on constitutive pigmentation and the skin's response to UV exposure (burning versus tanning).
Question 6: Which chemical sunscreen UV filter is the most common cause of photoallergic contact dermatitis in the United States?
- Zinc oxide
- Titanium dioxide
- Oxybenzone (benzophenone-3) (Correct answer)
- Avobenzone
Correct answer: Oxybenzone (benzophenone-3)
Oxybenzone (benzophenone-3) is the most frequent cause of sunscreen-related photoallergic contact dermatitis, identified in multiple patch-test surveillance studies.
ABD ABD Photodermatology and UV Effects 1
Which idiopathic photodermatosis is the most common, affecting up to 10-20% of the population in temperate climates?