Q.1 Which of the following is the most common idiopathic photodermatosis?
Polymorphic light eruption
Chronic actinic dermatitis
Solar urticaria
Hydroa vacciniforme
Explanation - Polymorphic light eruption (PMLE) is the most common idiopathic photodermatosis, typically affecting young women in spring or early summer.
Correct answer is: Polymorphic light eruption
Q.2 Solar urticaria is triggered mainly by exposure to which spectrum of light?
UVA
UVB
Visible light
Infrared
Explanation - Solar urticaria is most often triggered by visible light, although UVA and UVB can also play a role in some cases.
Correct answer is: Visible light
Q.3 Which photodermatosis is characterized by recurrent papules, vesicles, or plaques following sun exposure?
Chronic actinic dermatitis
Polymorphic light eruption
Solar urticaria
Porphyria cutanea tarda
Explanation - PMLE manifests as recurrent papules, vesicles, or plaques, usually occurring hours to days after sun exposure.
Correct answer is: Polymorphic light eruption
Q.4 Chronic actinic dermatitis is most commonly seen in which demographic group?
Young women
Elderly men
Children
Teenagers
Explanation - Chronic actinic dermatitis typically affects elderly men, presenting with persistent eczema-like lesions in sun-exposed areas.
Correct answer is: Elderly men
Q.5 Which diagnostic tool is most helpful in confirming photoallergic contact dermatitis?
Skin biopsy
Patch testing
Photopatch testing
Wood’s lamp examination
Explanation - Photopatch testing is used to diagnose photoallergic contact dermatitis by combining allergen exposure with controlled light irradiation.
Correct answer is: Photopatch testing
Q.6 Hydroa vacciniforme typically begins during which stage of life?
Infancy
Childhood
Adolescence
Adulthood
Explanation - Hydroa vacciniforme is a rare photodermatosis that usually begins in childhood and improves in adulthood.
Correct answer is: Childhood
Q.7 What is the hallmark clinical feature of solar urticaria?
Delayed onset papules
Immediate wheal and flare reaction
Chronic lichenified plaques
Blistering on sun exposure
Explanation - Solar urticaria presents with an immediate wheal and flare reaction within minutes of light exposure.
Correct answer is: Immediate wheal and flare reaction
Q.8 Porphyrias are photosensitive disorders due to defects in which pathway?
Keratin synthesis
Collagen metabolism
Heme biosynthesis
Melanin production
Explanation - Porphyrias result from enzyme defects in heme biosynthesis, leading to photosensitivity and blistering.
Correct answer is: Heme biosynthesis
Q.9 Which photodermatosis is associated with Epstein–Barr virus infection?
Hydroa vacciniforme
Polymorphic light eruption
Solar urticaria
Chronic actinic dermatitis
Explanation - Hydroa vacciniforme has been associated with latent Epstein–Barr virus infection in some cases.
Correct answer is: Hydroa vacciniforme
Q.10 Which vitamin deficiency can mimic features of photodermatoses?
Vitamin A
Vitamin B3
Vitamin D
Vitamin K
Explanation - Niacin (Vitamin B3) deficiency causes pellagra, which presents with photosensitive dermatitis among other features.
Correct answer is: Vitamin B3
Q.11 Which photodermatosis presents with persistent eczematous lesions exacerbated by sunlight?
Solar urticaria
Chronic actinic dermatitis
PMLE
Hydroa vacciniforme
Explanation - Chronic actinic dermatitis manifests as persistent eczematous plaques aggravated by light exposure.
Correct answer is: Chronic actinic dermatitis
Q.12 The action spectrum for polymorphic light eruption is mainly within which range?
UVA
UVB
Visible light
Infrared
Explanation - UVA radiation is the main trigger for PMLE, although UVB may also contribute.
Correct answer is: UVA
Q.13 Which immunologic mechanism is implicated in solar urticaria?
IgE-mediated hypersensitivity
T-cell mediated hypersensitivity
Immune complex deposition
Autoantibody formation
Explanation - Solar urticaria is thought to be mediated by IgE-dependent mechanisms against photo-induced antigens.
Correct answer is: IgE-mediated hypersensitivity
Q.14 Phototoxic reactions differ from photoallergic reactions in that they are:
Immunologically mediated
Dose dependent
Delayed hypersensitivity reactions
Not related to light exposure
Explanation - Phototoxic reactions are non-immunologic and dose dependent, while photoallergic reactions involve delayed hypersensitivity.
Correct answer is: Dose dependent
Q.15 Which photodermatosis shows vesicles and scars that resemble smallpox vaccination scars?
Solar urticaria
Hydroa vacciniforme
Polymorphic light eruption
Porphyria cutanea tarda
Explanation - Hydroa vacciniforme produces vesicles that heal with varioliform scarring, similar to vaccination marks.
Correct answer is: Hydroa vacciniforme
Q.16 The first-line treatment for solar urticaria is:
Topical corticosteroids
Systemic corticosteroids
Antihistamines
PUVA therapy
Explanation - Antihistamines are the mainstay treatment for solar urticaria to control wheal and flare reactions.
Correct answer is: Antihistamines
Q.17 Which photodermatosis may present with lichenified plaques due to chronic exposure?
Polymorphic light eruption
Solar urticaria
Chronic actinic dermatitis
Hydroa vacciniforme
Explanation - Chronic actinic dermatitis can progress to lichenified plaques from persistent inflammation.
Correct answer is: Chronic actinic dermatitis
Q.18 Which systemic drug is known to cause phototoxic reactions?
Doxycycline
Paracetamol
Atenolol
Prednisolone
Explanation - Tetracyclines, such as doxycycline, are classic culprits for phototoxic reactions.
Correct answer is: Doxycycline
Q.19 Which type of porphyria is most photosensitive?
Acute intermittent porphyria
Porphyria cutanea tarda
Hereditary coproporphyria
ALA dehydratase deficiency porphyria
Explanation - Porphyria cutanea tarda causes blistering photosensitivity on sun-exposed skin due to porphyrin accumulation.
Correct answer is: Porphyria cutanea tarda
Q.20 Which of the following is NOT a feature of polymorphic light eruption?
Onset in spring
Pruritic papules
Immediate reaction within minutes
Female predominance
Explanation - PMLE has a delayed onset of hours to days, unlike solar urticaria which occurs within minutes.
Correct answer is: Immediate reaction within minutes
Q.21 The term 'photodermatoses' refers to:
Skin disorders induced or aggravated by sunlight
Infectious skin diseases
Allergic skin reactions
Drug-induced rashes unrelated to light
Explanation - Photodermatoses are a group of conditions triggered or worsened by exposure to sunlight.
Correct answer is: Skin disorders induced or aggravated by sunlight
Q.22 Actinic prurigo is considered a chronic form of which condition?
Polymorphic light eruption
Solar urticaria
Chronic actinic dermatitis
Porphyria
Explanation - Actinic prurigo is regarded as a chronic form of PMLE with familial tendency.
Correct answer is: Polymorphic light eruption
Q.23 What is the most effective preventive strategy for photodermatoses?
Use of moisturizers
Strict photoprotection
Oral antibiotics
Immunotherapy
Explanation - Avoidance of sunlight and use of sunscreens are the most effective measures against photodermatoses.
Correct answer is: Strict photoprotection
Q.24 Which of the following tests is used to determine the minimal erythema dose?
Phototesting
Patch testing
Biopsy
Serology
Explanation - Phototesting determines the minimal erythema dose (MED) by exposing skin to graded doses of UV radiation.
Correct answer is: Phototesting
Q.25 Which photodermatosis is associated with immediate hives but no scarring?
Solar urticaria
Hydroa vacciniforme
PMLE
Porphyria cutanea tarda
Explanation - Solar urticaria produces hives that resolve without scarring, unlike hydroa vacciniforme.
Correct answer is: Solar urticaria