APPROACH TO PATIENT WITH SKIN DISORDER Flashcards
Which test is commonly used in the diagnosis of herpes simplex virus (HSV) and varicella-zoster virus (VZV) infections?
A) Wood’s lamp examination
B) Tzanck smear
C) Diascopy
D) Dermoscopy
Answer: B) Tzanck smear
Rationale: The Tzanck smear involves scraping the base of an early vesicle and staining it with Giemsa or Wright’s stain to detect multinucleated giant cells, which suggest HSV or VZV infection.
What type of lesion is best for performing a Tzanck smear?
A) Crusted lesion
B) Early vesicle
C) Pustule
D) Nodule
Answer: B) Early vesicle
Rationale: A fresh vesicle, not a pustule or crusted lesion, is unroofed for a Tzanck smear. The sample is taken from the base of the lesion to maximize the detection of multinucleated giant cells.
Which additional tests are required to confirm whether an HSV or VZV infection is present after a Tzanck smear?
A) PCR, culture, or immunofluorescence microscopy
B) Diascopy
C) Wood’s lamp examination
D) Biopsy with hematoxylin-eosin staining
Answer: A) PCR, culture, or immunofluorescence microscopy
Rationale: The Tzanck smear does not differentiate between HSV and VZV, so additional methods like PCR, viral culture, or immunofluorescence microscopy are needed for specific identification.
What is the purpose of diascopy in dermatologic evaluation?
A) To detect fungal infections
B) To differentiate between hemorrhagic and blood-filled lesions
C) To identify multinucleated giant cells
D) To evaluate pigmented lesions
Answer: B) To differentiate between hemorrhagic and blood-filled lesions
Rationale: Diascopy is performed by pressing a glass slide against the lesion. If the lesion blanches, it is blood-filled (e.g., urticaria). If it does not blanch, it suggests hemorrhage (e.g., purpura, vasculitis).
What is the characteristic appearance of granulomas on diascopy?
A) Coral pink fluorescence
B) “Apple jelly” brown-pink color
C) Yellow-green fluorescence
D) Deep blue discoloration
Answer: B) “Apple jelly” brown-pink color
Rationale: Granulomatous lesions, such as lupus vulgaris or sarcoidosis, show a brown-pink “apple jelly” appearance when examined using diascopy.
What is the primary function of dermoscopy?
A) To visualize deep skin infections
B) To assess whether lesions blanch under pressure
C) To examine pigmented lesions using magnification
D) To detect bacterial fluorescence under ultraviolet light
Answer: C) To examine pigmented lesions using magnification
Rationale: Dermoscopy uses a high-quality magnifying lens and a specialized light source to assess the structures, colors, and patterns of pigmented lesions, aiding in melanoma and nevus evaluation.
What skin condition exhibits a coral pink fluorescence under a Wood’s lamp?
A) Vitiligo
B) Erythrasma
C) Tinea capitis
D) Melanoma
Answer: B) Erythrasma
Rationale: Erythrasma, a superficial bacterial infection caused by Corynebacterium minutissimum, fluoresces coral pink under a Wood’s lamp.
Which dermatophyte species cause tinea capitis that fluoresces under a Wood’s lamp?
A) Trichophyton rubrum
B) Trichophyton mentagrophytes
C) Microsporum canis and Microsporum audouinii
D) Malassezia furfur
Answer: C) Microsporum canis and Microsporum audouinii
Rationale: Tinea capitis caused by Microsporum species (e.g., M. canis, M. audouinii) exhibits a yellow fluorescence under a Wood’s lamp. Trichophyton species usually do not fluoresce.
What characteristic feature does vitiligo show under a Wood’s lamp?
A) Deep red fluorescence
B) Coral pink fluorescence
C) Bright white or blue-white fluorescence
D) No visible change
Answer: C) Bright white or blue-white fluorescence
Rationale: Vitiligo lesions fluoresce bright white or blue-white under a Wood’s lamp due to the complete absence of melanin in the affected areas.
What type of biopsy technique involves using a circular blade rotated into the skin?
A) Excisional biopsy
B) Incisional biopsy
C) Punch biopsy
D) Shave biopsy
Answer: C) Punch biopsy
Rationale: A punch biopsy involves pressing and rotating a circular punch tool into the skin to obtain a full-thickness sample, including the epidermis, dermis, and sometimes subcutaneous fat.
What is the characteristic microscopic finding in tinea versicolor on KOH preparation?
A) Multinucleated giant cells
B) Gram-positive cocci in clusters
C) Spaghetti and meatballs appearance
D) Apple jelly nodules
Answer: C) Spaghetti and meatballs appearance
Rationale: Tinea versicolor, caused by Malassezia species, appears as a combination of round yeast cells (meatballs) and hyphae (spaghetti) under KOH preparation.
Which test is used to evaluate delayed hypersensitivity reactions to specific allergens?
A) Patch test
B) Prick test
C) Tzanck smear
D) KOH preparation
Answer: A) Patch test
Rationale: Patch testing identifies delayed hypersensitivity (Type IV hypersensitivity) reactions by applying suspected allergens to the skin under occlusive dressings and assessing for inflammation after 48 hours.
What is the typical duration for patch test allergens to remain in contact with the skin before evaluation?
A) 30 minutes
B) 12 hours
C) 24 hours
D) 48 hours
Answer: D) 48 hours
Rationale: Patch tests are left in place for 48 hours to allow delayed hypersensitivity reactions to develop. The site is then examined for erythema, edema, or vesicles.
