Dermatological Procedures Practice Questions

Q: Identify the type of skin graft?

Split thickness skin graft. ***Split thickness skin graft*** - This graft includes the **epidermis** and a **variable thickness of the dermis**, which allows the donor site to heal by re-epithelialization from the remaining adnexal structures. - It is the **most versatile** option for covering large surface area wounds as it provides a reliable take, though it has a higher tendency for secondary contraction and pigment dyschromia compared to full-thickness grafts. *Full-Thickness Skin Graft* - This graft contains the **entire epidermis** and **entire dermis**, which provides better durability, color match, and minimal wound contraction post-healing. - Due to the complete removal of the dermis, the donor site cannot heal spontaneously and requires **primary closure** or another skin graft. *Composite Graft* - This type of graft involves two or more tissue types (e.g., skin and cartilage) harvested as a single unit, often used for **nasal or ear reconstruction**. - It lacks an intrinsic blood supply and depends entirely on receiving revascularization from the host bed, limiting its size to usually **less than 1 cm** to ensure survival. *Biomesh* - This is a **biological scaffold** or extracellular matrix (ECM) derived from human or animal tissue rather than a traditional skin graft. - It is primarily used for **tissue regeneration** and hernia repair rather than surface coverage of skin defects.

Q: A child presents with erythematous, non-blanching, bosselated lesions on the left side of the face. What is the treatment of choice?

Flash light-pumped dye laser. ### Explanation **Correct Answer: C. Flash light-pumped dye laser (FPDL)** The clinical description—erythematous, non-blanching, bosselated (bumpy/lobulated) lesions—is characteristic of a **Port-Wine Stain (PWS)** or a **Capillary Malformation**. The **Flash light-pumped pulsed dye laser (FPDL)**, typically at a wavelength of **585 nm or 595 nm**, is the gold standard treatment for vascular lesions like PWS. It operates on the principle of **selective photothermolysis**. The laser energy is specifically absorbed by **oxyhemoglobin** (the chromophore) within the blood vessels, leading to thermal destruction of the vessel walls while sparing the surrounding skin. This minimizes scarring, making it ideal for pediatric facial lesions. **Analysis of Incorrect Options:** * **A. Erbium:YAG Laser (2940 nm):** This is an ablative laser used primarily for skin resurfacing and removing benign epidermal growths. It targets water, not hemoglobin. * **B. Nd:YAG Laser (1064 nm):** While used for deeper vascular malformations due to its high penetration depth, it carries a higher risk of scarring and is not the first-line "treatment of choice" for superficial PWS. * **D. Q-switched Ruby Laser (694 nm):** This is primarily used for pigmentary disorders (like Nevus of Ota) and black/blue tattoo removal. It targets melanin, not vascular structures. **Clinical Pearls for NEET-PG:** * **Chromophore for Vascular Lasers:** Oxyhemoglobin. * **Chromophore for Pigment/Tattoo Lasers:** Melanin/Exogenous ink. * **Port-Wine Stains:** Unlike strawberry hemangiomas, PWS do not involute spontaneously; they grow proportionately with the child and may become "bosselated" or hypertrophic over time. * **Sturge-Weber Syndrome:** Always rule this out if a PWS involves the V1/V2 distribution of the trigeminal nerve.

Q: Patch test is done to document which type of hypersensitivity?

Delayed type hypersensitivity. ### Explanation **Correct Answer: B. Delayed type hypersensitivity** The **Patch Test** is the gold standard diagnostic tool for **Allergic Contact Dermatitis (ACD)**. ACD is a classic example of **Type IV Hypersensitivity** (also known as Delayed-type Hypersensitivity). * **Mechanism:** This reaction is **T-cell mediated** (specifically Th1 cells). When an allergen is applied to the skin, it is processed by Langerhans cells and presented to memory T-cells. This process takes time, which is why the test results are typically read at **48 hours** (initial reading) and **72–96 hours** (delayed reading). **Why other options are incorrect:** * **Type I Hypersensitivity (Option A):** This is IgE-mediated (immediate). It is tested using the **Skin Prick Test** or RAST, used for conditions like urticaria or asthma. * **Autoimmune disease (Option C):** While some skin diseases are autoimmune (e.g., Pemphigus), they are diagnosed via biopsy and Direct Immunofluorescence (DIF), not patch testing. * **Immunocomplex deposition (Option D):** This refers to **Type III Hypersensitivity** (e.g., SLE or Vasculitis), which involves antigen-antibody complexes depositing in tissues. **High-Yield Clinical Pearls for NEET-PG:** * **Standard Series:** The most common series used globally is the **European Standard Series**. * **Common Allergens:** The most common allergen globally is **Nickel** (found in artificial jewelry). * **Reading Results:** * (+) = Erythema and edema. * (++) = Erythema, edema, and papulovesicles. * (+++) = Confluent vesicles or bullae. * **Open Patch Test:** Used for testing substances with potential irritancy (e.g., shampoos). * **Photopatch Test:** Used for Photoallergic Contact Dermatitis (e.g., reactions to NSAIDs or sunscreens).

Q: All of the following are used in cryosurgery except?

Helium. **Explanation:** Cryosurgery involves the controlled destruction of unwanted tissue by the application of extreme cold. The efficacy of a cryogen depends on its boiling point; the lower the boiling point, the more effective it is at causing rapid tissue necrosis. **Why Helium is the correct answer:** Helium is **not** used as a cryogen in clinical dermatology. While liquid helium has an extremely low boiling point (-268.9°C), it is technically difficult to store, prohibitively expensive, and lacks the practical delivery systems required for cutaneous surgery. In medical contexts, helium is more commonly used in "Heliox" mixtures for respiratory distress or as a coolant for MRI magnets, but not for cryosurgery. **Analysis of other options:** * **Liquid Nitrogen (A):** The "Gold Standard" in cryosurgery. It has a boiling point of **-195.8°C**. It is the most commonly used agent due to its high efficacy in treating both benign and malignant lesions. * **Argon (B):** Used primarily in **cryoablation probes** (often for internal tumors like prostate or renal cell carcinoma) via the Joule-Thomson effect. * **Carbon Dioxide (D):** Used as "CO2 snow" or via specialized probes. It has a temperature of **-78.5°C**. While less potent than liquid nitrogen, it was historically popular for treating acne and hemangiomas. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Damage:** Cryosurgery causes cell death via ice crystal formation (intracellular), vascular stasis, and protein denaturation. * **Temperature Thresholds:** Benign lesions require -20°C to -30°C; Malignant lesions require -40°C to -50°C. * **Melanocyte Sensitivity:** Melanocytes are highly sensitive to cold (-4°C to -7°C), which is why **permanent hypopigmentation** is a common side effect of cryotherapy. * **Nitrous Oxide (-89.5°C):** Another common cryogen used in portable "cryo-pens."

Q: What is the wavelength of light produced by a Wood's lamp?

360 nm. **Explanation:** A **Wood’s lamp** is a diagnostic tool that emits long-wave ultraviolet radiation (UVA). It utilizes a high-pressure mercury arc light source filtered through a **Wood’s filter** (composed of barium silicate with 9% nickel oxide). This filter is opaque to all light rays except for a specific band, peaking at **360 nm** (range 320–400 nm). When this light hits certain structures (fluorophores), they emit visible light of a longer wavelength, resulting in characteristic fluorescence. **Analysis of Options:** * **B (360 nm):** This is the peak wavelength emitted by the Wood's lamp. It falls within the UVA spectrum and is the standard value tested in medical examinations. * **A (320 nm):** This represents the lower limit of the UVA spectrum and the cutoff for the Wood's filter, but it is not the peak emission wavelength. * **C (400 nm):** This is the upper limit of the UV spectrum where it transitions into visible violet light. * **D (760-800 nm):** This range corresponds to **Infrared light**, which is used in heat therapy, not diagnostic fluorescence. **High-Yield Clinical Pearls for NEET-PG:** * **Tinea Capitis:** *Microsporum* species show **Bright Green** fluorescence (due to Pteridine). Note: *Trichophyton tonsurans* (common cause of endothrix) does **not** fluoresce. * **Erythrasma:** Caused by *Corynebacterium minutissimum*; shows **Coral Red** fluorescence (due to Coproporphyrin III). * **Porphyria Cutanea Tarda:** Urine shows **Pink-Orange** fluorescence. * **Pseudomonas:** Shows **Yellow-Green** fluorescence (due to Pyoverdin). * **Vitiligo:** Shows **Milky White** fluorescence (due to total loss of melanin, which normally absorbs UV light).

Q: Which of the following is not an agent used in chemical peeling?

Kojic acid. In chemical peeling, specific chemical agents are applied to the skin to cause controlled destruction of a portion of the epidermis and/or dermis, leading to exfoliation and subsequent regeneration of new tissues. **Why Kojic Acid is the correct answer:** While **Kojic acid** is a common ingredient in dermatological practice, it is classified as a **skin-lightening (depigmenting) agent**, not a primary peeling agent. It works by inhibiting tyrosinase, the enzyme responsible for melanin synthesis. It is frequently used as an adjuvant in "pre-peel" priming creams or post-procedure maintenance to treat hyperpigmentation, but it does not possess the keratolytic or caustic properties required to induce a chemical peel on its own. **Analysis of incorrect options:** * **Glycolic acid (A):** An Alpha-hydroxy acid (AHA) derived from sugarcane. It is the most common agent used for **superficial peels**. * **Phenol (C):** A potent agent used for **deep peels**. It causes protein coagulation and can reach the reticular dermis; however, it requires cardiac monitoring due to potential systemic toxicity (arrhythmias). * **Salicylic acid (D):** A Beta-hydroxy acid (BHA). It is lipophilic, making it the agent of choice for **acne-prone skin** as it can penetrate the sebaceous unit. **High-Yield Clinical Pearls for NEET-PG:** * **Jessner’s Solution:** A popular combination peel containing Salicylic acid (14g), Lactic acid (14g), and Resorcinol (14g) in Ethanol. * **Trichloroacetic acid (TCA):** Used for medium-depth peels. The "frosting" seen during the procedure is due to protein denaturation. * **Priming:** Patients are often started on Tretinoin or Hydroquinone 2–4 weeks before a peel to ensure uniform penetration and prevent post-inflammatory hyperpigmentation (PIH).

Q: Mohs micrographic excision for basal cell carcinoma is used for all of the following indications except:

Tumor less than 2 cm in diameter. **Explanation:** Mohs Micrographic Surgery (MMS) is a specialized surgical technique designed to provide the highest possible cure rate while maximizing tissue conservation. The core principle of MMS is the **100% evaluation of peripheral and deep surgical margins** through horizontal sectioning while the patient waits. **Why Option B is the correct answer:** Size alone is not an absolute indication for Mohs surgery. In fact, **tumors larger than 2 cm** (especially in the "M" or "H" zones of the face) are considered high-risk and are primary indications for MMS. A small tumor (<2 cm) with non-aggressive histology in a low-risk area (like the trunk or extremities) is typically treated with standard wide local excision, as Mohs would be unnecessarily resource-intensive. **Analysis of Incorrect Options:** * **A. Recurrent tumor:** Recurrent BCCs often have unpredictable "finger-like" extensions and subclinical spread, making Mohs the gold standard to ensure complete removal. * **C. Aggressive histology:** Subtypes like morpheaform, infiltrative, or micronodular BCC have higher rates of local recurrence and require the precise margin control offered by Mohs. * **D. Perineural invasion:** This indicates a high risk of tracking along nerve sheaths far beyond the visible tumor border, necessitating microscopic mapping. **High-Yield Clinical Pearls for NEET-PG:** * **Indications for Mohs (The "H" Zone):** High-risk areas include the "Mask area" of the face (eyelids, nose, lips, ears, temples). * **Tissue Sparing:** It is the treatment of choice for areas where cosmesis and function are critical (e.g., digits, genitalia). * **Cure Rate:** MMS offers a 99% cure rate for primary BCC and 94-96% for recurrent BCC. * **Key Difference:** Unlike standard pathology (vertical "bread-loafing" which examines <1% of margins), Mohs examines **100% of the margin.**

Q: Tzanck preparation is used for the diagnosis of which of the following skin conditions, EXCEPT?

Fungal infections. ### Explanation The **Tzanck smear** is a rapid bedside diagnostic test used primarily to identify **acantholytic cells** (Tzanck cells) and multinucleated giant cells. It involves taking a scraping from the base of a fresh vesicle or bulla. **Why Fungal Infections is the Correct Answer:** Tzanck preparation is not used for diagnosing fungal infections. The gold standard bedside test for fungal elements (hyphae, spores, or budding yeast) is a **KOH (Potassium Hydroxide) mount**, which dissolves keratin to visualize the fungi. Tzanck smear lacks the specific stains or chemical properties required to identify fungal morphology effectively. **Analysis of Other Options:** * **Pemphigus (Option A):** This is the classic indication for a Tzanck smear. It reveals **acantholytic cells** (rounded keratinocytes with hyperchromatic nuclei) due to the loss of intercellular adhesion. * **Stevens-Johnson Syndrome (Option B):** In SJS/TEN, a Tzanck smear shows **necrotic keratinocytes** and inflammatory cells, helping to differentiate it from staphylococcal scalded skin syndrome (SSSS). * **Senear-Usher Syndrome (Option C):** Also known as **Pemphigus Erythematosus**, it is a localized variant of Pemphigus Foliaceus. Since it is an immunobullous disease characterized by acantholysis, Tzanck cells will be present. **High-Yield Clinical Pearls for NEET-PG:** 1. **Herpes Simplex/Varicella Zoster:** Tzanck smear shows **Multinucleated Giant Cells** (with Cowdry A inclusion bodies). 2. **Molluscum Contagiosum:** Shows large, oval, eosinophilic cytoplasmic inclusion bodies known as **Henderson-Paterson bodies**. 3. **Donovanosis (Granuloma Inguinale):** Shows **Donovan bodies** (safety-pin appearance) within macrophages. 4. **Staphylococcal Scalded Skin Syndrome (SSSS):** Tzanck smear shows acantholytic cells (similar to Pemphigus), but the cleavage is more superficial (subcorneal).

Question 1

Identify the type of skin graft?

Accepted Answer

Split thickness skin graft

Answer

Full-Thickness Skin Graft

Answer

Composite Graft

Answer

Biomesh

Question 2

Which of the following is NOT true regarding patch testing?

Accepted Answer

False negative results can occur in patients with angry back syndrome

Answer

Used to diagnose allergic contact dermatitis

Answer

Readings are typically taken after 48 hours

Answer

The T.R.U.E. test is a type of patch test

Question 3

A child presents with erythematous, non-blanching, bosselated lesions on the left side of the face. What is the treatment of choice?

Accepted Answer

Flash light-pumped dye laser

Answer

Erbium laser

Answer

Nd-YAG laser

Answer

Q-switched ruby laser

Question 4

Patch test is done to document which type of hypersensitivity?

Accepted Answer

Delayed type hypersensitivity

Answer

Type I hypersensitivity

Answer

Autoimmune disease

Answer

Immunocomplex deposition

Question 5

All of the following are used in cryosurgery except?

Accepted Answer

Helium

Answer

Liquid nitrogen

Answer

Argon

Answer

Carbon dioxide

Question 6

What is the wavelength of light produced by a Wood's lamp?

Accepted Answer

360 nm

Answer

320 nm

Answer

400 nm

Answer

760-800 nm

Question 7

Which of the following is not an agent used in chemical peeling?

Accepted Answer

Kojic acid

Answer

Glycolic acid

Answer

Phenol

Answer

Salicylic acid

Question 8

What is the mechanism by which the following technique works?

Accepted Answer

Negative pressure

Answer

Cryotherapy

Answer

Positive pressure

Answer

Sclerotherapy

Question 9

Mohs micrographic excision for basal cell carcinoma is used for all of the following indications except:

Accepted Answer

Tumor less than 2 cm in diameter

Answer

Recurrent tumor

Answer

Tumors with aggressive histology

Answer

Tumors with perineural invasion

Question 10

Tzanck preparation is used for the diagnosis of which of the following skin conditions, EXCEPT?

Accepted Answer

Fungal infections

Answer

Pemphigus

Answer

Stevens-Johnson syndrome

Answer

Senear-Usher syndrome

Dermatological Procedures — MCQs

Dermatological Procedures — MCQs

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