COMSAE Dermatology and Integumentary System — Questions and Answers
Question 1: A 16-year-old presents with open and closed comedones, papules, and pustules on the face. Which mechanism is most responsible for the pathogenesis of acne vulgaris?
- Autoimmune destruction of sebaceous glands
- Follicular plugging with keratin and sebum combined with Cutibacterium acnes proliferation (Correct answer)
- Staphylococcus aureus superficial skin infection
- IgE-mediated mast cell degranulation in the dermis
Correct answer: Follicular plugging with keratin and sebum combined with Cutibacterium acnes proliferation
Acne vulgaris results from follicular hyperkeratinization causing plugging, excess sebum production, C. acnes overgrowth, and resultant inflammation.
Question 2: A 45-year-old presents with well-demarcated, erythematous plaques with silvery-white scales on the elbows and scalp. Auspitz sign is positive. Which finding on histopathology is most characteristic of this condition?
- Spongiosis with eosinophilic infiltrate
- Parakeratosis with neutrophils in the stratum corneum (Munro microabscesses) (Correct answer)
- Acantholysis with suprabasal blistering
- Hyperkeratosis with melanin incontinence
Correct answer: Parakeratosis with neutrophils in the stratum corneum (Munro microabscesses)
Psoriasis classically shows parakeratosis, acanthosis, elongated rete ridges, and Munro microabscesses (neutrophils in the stratum corneum).
Question 3: Which of the following ABCDE features of a pigmented skin lesion is MOST associated with early melanoma detection?
- A uniform tan color throughout the lesion
- Border that is well-defined and regular
- Asymmetry — one half does not match the other (Correct answer)
- Diameter less than 6 mm
Correct answer: Asymmetry — one half does not match the other
Asymmetry is a hallmark of melanoma; benign nevi are typically symmetric, whereas melanoma grows irregularly in different directions.
Question 4: A 32-year-old factory worker develops pruritic vesicles and erythema on both hands after starting a new job using epoxy resins. Patch testing shows a reaction to epoxy resin. What type of hypersensitivity reaction is this?
- Type I (IgE-mediated)
- Type II (cytotoxic)
- Type III (immune complex-mediated)
- Type IV (delayed-type/cell-mediated) (Correct answer)
Correct answer: Type IV (delayed-type/cell-mediated)
Allergic contact dermatitis is a classic Type IV (delayed-type) hypersensitivity reaction mediated by sensitized T lymphocytes, peaking 48–72 hours after exposure.
Question 5: A 22-year-old athlete presents with scaling, itching, and erythema between the toes with maceration. KOH preparation shows branching hyphae. Which organism is most likely responsible?
- Candida albicans
- Trichophyton rubrum (Correct answer)
- Malassezia furfur
- Microsporum canis
Correct answer: Trichophyton rubrum
Tinea pedis (athlete's foot) is most commonly caused by Trichophyton rubrum, a dermatophyte that infects keratinized tissue.
Question 6: A 6-year-old with a family history of asthma and allergic rhinitis presents with intensely pruritic, erythematous, lichenified patches in the antecubital and popliteal fossae. Which immunological finding is most commonly elevated in this condition?
- IgA
- IgG
- IgE (Correct answer)
- IgM
Correct answer: IgE
Atopic dermatitis is associated with elevated serum IgE levels and Th2-predominant immune responses, often part of the atopic triad.
Question 7: A 65-year-old with a history of heavy sun exposure presents with a pearly, translucent nodule with rolled borders and telangiectasias on the nose. Which is the most likely diagnosis?
- Squamous cell carcinoma
- Melanoma
- Basal cell carcinoma (Correct answer)
- Keratoacanthoma
Correct answer: Basal cell carcinoma
Basal cell carcinoma classically presents as a pearly papule or nodule with rolled borders and telangiectasias on sun-exposed areas, especially the nose.
Question 8: A 40-year-old woman presents with facial flushing, erythema across the nose and cheeks, telangiectasias, and papulopustules. She reports flares with sun exposure, hot beverages, and alcohol. Which diagnosis is most likely?
- Systemic lupus erythematosus
- Rosacea (Correct answer)
- Perioral dermatitis
- Seborrheic dermatitis
Correct answer: Rosacea
Rosacea is characterized by central facial erythema, flushing, telangiectasias, and papulopustules triggered by heat, alcohol, spicy food, and UV exposure.
Question 9: A 50-year-old presents with greasy, yellowish scales on the scalp, nasolabial folds, and eyebrows. Which organism is implicated in the pathogenesis of seborrheic dermatitis?
- Staphylococcus epidermidis
- Malassezia furfur (Correct answer)
- Trichophyton tonsurans
- Candida albicans
Correct answer: Malassezia furfur
Malassezia furfur (a lipophilic yeast) colonizes sebaceous areas and triggers an inflammatory response causing seborrheic dermatitis.
Question 10: A 70-year-old farmer presents with an indurated, erythematous nodule on the lower lip that ulcerates and does not heal. Biopsy shows malignant squamous cells with keratin pearls. Which risk factor is most strongly associated with this diagnosis?
- BRCA1 gene mutation
- Chronic UV radiation exposure (Correct answer)
- Human papillomavirus type 16 infection
- Immunosuppression from organ transplant
Correct answer: Chronic UV radiation exposure
Squamous cell carcinoma of the lip and skin is most strongly associated with chronic UV radiation exposure, particularly in fair-skinned, outdoor workers.
Question 11: A 28-year-old develops widespread pruritic wheals of various sizes that resolve within 24 hours without leaving bruising or scarring. She denies systemic symptoms. Which mechanism is responsible?
- T-cell mediated cytotoxicity
- IgE-mediated mast cell degranulation releasing histamine (Correct answer)
- Immune complex deposition in dermal vessels
- Complement-mediated lysis of keratinocytes
Correct answer: IgE-mediated mast cell degranulation releasing histamine
Urticaria is caused by IgE-mediated mast cell degranulation releasing histamine and other mediators, causing transient wheals that resolve without trace.
Question 12: A 19-year-old started trimethoprim-sulfamethoxazole for a urinary tract infection. Three weeks later she develops widespread erythematous targetoid lesions involving mucosal surfaces, with epidermal detachment >30% of the body surface area. Which condition best describes this presentation?
- Erythema multiforme major
- Toxic epidermal necrolysis (TEN) (Correct answer)
- Pemphigus vulgaris
- Bullous pemphigoid
Correct answer: Toxic epidermal necrolysis (TEN)
Toxic epidermal necrolysis (TEN) is a severe drug reaction with epidermal detachment >30% BSA and mucosal involvement, most commonly triggered by sulfonamides and anticonvulsants.
Question 13: A 60-year-old presents with a rough, scaly, erythematous macule on the dorsum of the hand. The lesion is described as a premalignant condition with potential to progress to squamous cell carcinoma. Which is the most likely diagnosis?
- Seborrheic keratosis
- Actinic keratosis (Correct answer)
- Lentigo simplex
- Dermatofibroma
Correct answer: Actinic keratosis
Actinic keratosis is a premalignant lesion caused by chronic UV exposure that can progress to squamous cell carcinoma if untreated.
Question 14: A 35-year-old presents with flaccid bullae that rupture easily, leaving raw erosions. The Nikolsky sign is positive. Direct immunofluorescence shows IgG deposits in a 'fishnet' pattern throughout the epidermis. Which diagnosis is most likely?
- Bullous pemphigoid
- Pemphigus vulgaris (Correct answer)
- Dermatitis herpetiformis
- Linear IgA bullous dermatosis
Correct answer: Pemphigus vulgaris
Pemphigus vulgaris is characterized by IgG autoantibodies against desmoglein 1 and 3, causing suprabasal acantholysis, flaccid bullae, and a positive Nikolsky sign.
Question 15: A 25-year-old woman notices well-circumscribed patches of hair loss on the scalp. Examination reveals smooth scalp skin with 'exclamation point' hairs at the periphery of patches. Which is the most likely diagnosis?
- Androgenetic alopecia
- Tinea capitis
- Alopecia areata (Correct answer)
- Traction alopecia
Correct answer: Alopecia areata
Alopecia areata is an autoimmune condition causing well-demarcated patches of non-scarring hair loss with characteristic 'exclamation point' hairs at patch margins.
Question 16: A 70-year-old presents with tense bullae on the trunk and extremities. The Nikolsky sign is negative. Direct immunofluorescence shows linear IgG and C3 deposits at the dermoepidermal junction. Which is the most likely diagnosis?
- Pemphigus vulgaris
- Dermatitis herpetiformis
- Bullous pemphigoid (Correct answer)
- Epidermolysis bullosa acquisita
Correct answer: Bullous pemphigoid
Bullous pemphigoid features tense subepidermal bullae with linear IgG/C3 at the BMZ, targeting BP180 and BP230 antigens; the Nikolsky sign is negative.
Question 17: A 30-year-old develops target-shaped lesions (concentric rings) on the palms and soles after a recent herpes simplex virus infection. There is no mucosal involvement. Which condition does this most likely represent?
- Stevens-Johnson syndrome
- Erythema multiforme minor (Correct answer)
- Toxic epidermal necrolysis
- Fixed drug eruption
Correct answer: Erythema multiforme minor
Erythema multiforme minor presents with classic targetoid lesions, typically triggered by HSV or Mycoplasma pneumoniae, without significant mucosal or systemic involvement.
Question 18: A 45-year-old immigrant presents with intense nocturnal pruritus. Examination reveals burrows in the finger web spaces and erythematous papules on the wrists and genitalia. Which pathogen is responsible?
- Pediculus humanus capitis
- Sarcoptes scabiei (Correct answer)
- Demodex folliculorum
- Phthirus pubis
Correct answer: Sarcoptes scabiei
Scabies is caused by Sarcoptes scabiei mite infestation; characteristic features are intense nocturnal pruritus, burrows in interdigital spaces, and involvement of genitalia.
Question 19: A 65-year-old presents with a dermatomal distribution of painful vesicles on an erythematous base on the right thorax. She had varicella as a child. Which antiviral should be initiated within 72 hours of onset?
- Oseltamivir
- Acyclovir (Correct answer)
- Ganciclovir
- Amantadine
Correct answer: Acyclovir
Herpes zoster (shingles) results from VZV reactivation; antiviral therapy with acyclovir, valacyclovir, or famciclovir within 72 hours reduces duration and risk of postherpetic neuralgia.
Question 20: A 22-year-old presents with well-defined depigmented macules on the dorsum of hands, around the mouth, and on the genitalia. Wood's lamp examination shows chalk-white fluorescence. The macules are asymptomatic. Which is the most likely diagnosis?
- Albinism
- Pityriasis versicolor
- Vitiligo (Correct answer)
- Tinea corporis
Correct answer: Vitiligo
Vitiligo is an autoimmune condition causing melanocyte destruction, producing well-defined depigmented macules that fluoresce bright white under Wood's lamp.
Question 21: A 55-year-old diabetic presents with rapidly spreading erythema, warmth, swelling, and tenderness of the lower leg with a distinct raised, palpable border and fever. Which condition most likely explains the palpable, sharply demarcated border?
- Cellulitis involving the deep dermis and subcutaneous tissue
- Erysipelas involving the superficial dermis and lymphatics (Correct answer)
- Necrotizing fasciitis involving fascia and muscle
- Folliculitis involving hair follicles
Correct answer: Erysipelas involving the superficial dermis and lymphatics
Erysipelas involves the superficial dermis and dermal lymphatics, producing a sharply demarcated, raised, palpable border that distinguishes it from the indistinct borders of deeper cellulitis.
COMSAE Dermatology and Integumentary System
A 16-year-old presents with open and closed comedones, papules, and pustules on the face.
Which mechanism is most responsible for the pathogenesis of acne vulgaris?
What Practice Test Geeks adds beyond an AI chat for COMSAE
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Sources & references
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