COMSAE Dermatology and Integumentary System 1 — 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.
COMSAE Dermatology and Integumentary System 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?