Basic Dermatology Practice Questions

Q: Keloid formation is not typically seen over which of the following areas?

Eyelids. **Explanation:** Keloids are benign fibroproliferative growths resulting from an exaggerated healing response to skin injury. They are characterized by the excessive deposition of Type I and Type III collagen that extends **beyond the boundaries** of the original wound. **Why Eyelids are the Correct Answer:** Keloid formation is highly dependent on skin tension and the density of skin appendages. The **eyelids**, along with the **penis, scrotum, palms, and soles**, are considered "immune" or highly resistant to keloid formation. This is primarily due to the extreme laxity of the skin and the lack of high dermal tension in these regions. **Analysis of Incorrect Options:** * **Ear:** The earlobes are one of the most common sites for keloids, often triggered by ear piercing. * **Face:** While less common than the chest, keloids can occur on the face, particularly along the jawline (often associated with acne or folliculitis barbae). * **Neck:** The anterior and lateral neck are high-tension areas prone to hypertrophic scars and keloids following trauma or surgical procedures. **Clinical Pearls for NEET-PG:** 1. **Commonest Site:** The **presternal area** (over the sternum) is the most common site due to high constant skin tension. Other common sites include the deltoid region and upper back. 2. **Histology:** Characterized by thick, eosinophilic, "glassy" collagen bundles (hyalinized collagen). 3. **Treatment:** Intralesional **Triamcinolone acetonide** (corticosteroid) is the first-line treatment. 4. **Key Difference:** Unlike hypertrophic scars, keloids do not regress spontaneously and extend beyond the original margin of injury.

Q: All of the following are primary lesions of the skin except:

Scar. **Explanation:** In dermatology, skin lesions are categorized into **Primary Lesions** (those that develop as a direct result of the disease process) and **Secondary Lesions** (those that evolve from primary lesions due to evolution, trauma, or treatment). **Why Scar is the correct answer:** A **Scar** is a **Secondary Lesion**. It represents the replacement of normal skin by fibrous connective tissue (collagen) following an injury to the dermis. Since it is a result of the healing process rather than the initial manifestation of a disease, it is classified as secondary. **Analysis of Incorrect Options:** * **Nodule:** A **Primary Lesion**. It is a solid, palpable, circumscribed elevation >0.5 cm in diameter, involving the deeper dermis or subcutaneous tissue. * **Purpura:** A **Primary Lesion**. It refers to discoloration caused by the extravasation of red blood cells into the skin. Smaller lesions ( 5mm) are ecchymoses. * **Wheal:** A **Primary Lesion**. It is a transient, edematous, circumscribed plaque (e.g., Urticaria) caused by dermal edema. **NEET-PG High-Yield Pearls:** * **Primary Lesions:** Macule, Papule, Patch, Plaque, Nodule, Vesicle, Bulla, Pustule, Wheal, and Purpura. * **Secondary Lesions:** Scale, Crust, Erosion, Ulcer, Fissure, Atrophy, **Scar**, and Lichenification. * **Memory Aid:** If the lesion is the "first" thing you see in a disease, it’s primary. If it’s what happens "after" (healing, scratching, or infection), it’s secondary. * **Note:** Some textbooks classify Purpura as a "special" primary lesion, but it is never classified as secondary.

Q: Necrotic keratinocytes are typically seen in which of the following conditions?

All of the above. **Explanation:** The presence of **necrotic keratinocytes** (also known as apoptotic keratinocytes, Civatte bodies, or colloid bodies) is a hallmark of **Interface Dermatitis**. This histological pattern is characterized by damage to the basal layer of the epidermis, leading to keratinocyte death. 1. **Erythema Multiforme (EM):** This is the classic example of acute interface dermatitis. It shows prominent individual cell necrosis throughout the epidermis, which can progress to full-thickness epidermal necrosis in severe cases (like Stevens-Johnson Syndrome). 2. **Graft Versus Host Disease (GVHD):** In acute GVHD, cytotoxic T-cells attack host keratinocytes, leading to "satellite cell necrosis" (lymphocytes closely associated with necrotic keratinocytes). 3. **Discoid Lupus Erythematosus (DLE):** This represents a chronic form of interface dermatitis. It features vacuolar degeneration of the basal layer and the presence of necrotic keratinocytes (Civatte bodies) at the dermo-epidermal junction. **Clinical Pearls for NEET-PG:** * **Civatte Bodies:** These are eosinophilic, PAS-positive remnants of dead keratinocytes found in the lower epidermis or papillary dermis. * **Differential Diagnosis of Interface Dermatitis:** Remember the mnemonic **"L-E-G"**: **L**ichen Planus, **E**rythema Multiforme/Lupus **E**rythematosus, and **G**raft vs. Host Disease. * **Lichen Planus:** While it also shows necrotic keratinocytes, the hallmark is a "saw-tooth" appearance of rete ridges and a band-like lymphocytic infiltrate. * **High-Yield Fact:** If the question mentions "Satellite Cell Necrosis," think specifically of **GVHD**.

Q: The pustular, neutrophil-rich skin lesions that develop or worsen following intradermal trauma is called what?

Pathergy. **Explanation:** The correct answer is **Pathergy**. **1. Why Pathergy is Correct:** Pathergy refers to an exaggerated skin inflammatory response to minor trauma (such as a needle prick). Clinically, it manifests as the development of a papule or sterile pustule 24–48 hours after an intradermal insult. Histologically, these lesions are characterized by a dense **neutrophilic infiltrate**. This phenomenon is a hallmark diagnostic criterion for **Behçet’s disease** and is also frequently observed in **Pyoderma gangrenosum** and Sweet syndrome. **2. Why Other Options are Incorrect:** * **Erythema nodosum (A):** This is a form of septal panniculitis presenting as tender, erythematous nodules, typically on the shins. It is a hypersensitivity reaction but is not triggered by intradermal trauma. * **Koebner Phenomenon (B):** Also known as the "isomorphic response," this refers to the development of **new lesions of a pre-existing dermatosis** (like Psoriasis, Vitiligo, or Lichen Planus) at the site of trauma. Unlike pathergy, it does not specifically result in a sterile pustule and takes longer (7–14 days) to appear. * **Dermatitis herpetiformis (D):** This is an autoimmune blistering disorder associated with Celiac disease, characterized by intensely pruritic vesicles on extensor surfaces and IgA deposits in dermal papillae. It is not trauma-induced. **Clinical Pearls for NEET-PG:** * **Pathergy Test:** Performed using a 20-gauge needle; positive if a >2mm indurated papule/pustule forms. * **Differential Diagnosis:** While Pathergy = Behçet’s/Pyoderma gangrenosum, **Pseudo-pathergy** can be seen in Sweet syndrome. * **High-Yield Distinction:** Koebner = "Same lesion as disease" (e.g., scale in Psoriasis); Pathergy = "Sterile pustule/hyper-reactivity."

Q: What is the approximate number of bacteria per square centimeter of skin?

10^2 - 10^3. **Explanation:** The human skin is a vast ecosystem harboring a diverse population of microorganisms, collectively known as the **skin microbiome**. On average, the bacterial density across the general surface of the skin is approximately **10² to 10³ (100 to 1,000) organisms per square centimeter**. The correct answer is **B** because while the total number of bacteria on the entire human body is estimated to be around $10^{12}$, the distribution per unit area is relatively sparse in "dry" zones (like the forearms or trunk) compared to other body sites. **Analysis of Incorrect Options:** * **Option A (10¹ - 10²):** This value is too low. Even the driest areas of the skin typically maintain a colonization density higher than 100 organisms/cm². * **Option C (10⁵ - 10¹⁰) & Option D (>10⁷):** These values represent extreme colonization. While densities can reach $10^6$ to $10^7$ in high-moisture, sebum-rich areas (like the axilla, groin, or toe webs), they do not represent the "average" skin surface density. Values above $10^5$ are often associated with clinical infection or heavy biofilm formation in specific niches. **High-Yield Clinical Pearls for NEET-PG:** * **Regional Variation:** Bacterial density is highest in **intertriginous areas** (axilla, groin) and lowest on dry, exposed skin. * **Resident vs. Transient Flora:** *Staphylococcus epidermidis* (Coagulase-negative Staph) and *Corynebacterium* species are the most common **resident** bacteria. *Staphylococcus aureus* is usually considered **transient** or a colonizer in pathological states (e.g., Atopic Dermatitis). * **Skin pH:** The "Acid Mantle" (pH 4.5–5.5) is a crucial innate defense mechanism that limits the overgrowth of pathogenic bacteria. * **Commonest Fungus:** *Malassezia* species are the most prevalent resident fungi on adult skin, particularly in sebaceous areas.

Q: Blaschko's lines refers to lines of what developmental process?

Ectodermal cell migration. **Explanation:** **Blaschko’s lines** represent a fundamental concept in cutaneous embryology and genetics. They are non-random patterns on the skin that do not correspond to nervous, muscular, or lymphatic pathways. 1. **Why Option B is Correct:** Blaschko’s lines represent the pathways of **ectodermal cell migration** and proliferation during embryonic development. They reflect the clonal expansion of keratinocytes and melanocytes (both derived from the ectoderm/neural crest) as they migrate from the neural crest and primitive streak. When a mutation occurs in a single cell during early development, the progeny of that cell follow these lines, resulting in **cutaneous mosaicism**. 2. **Why Other Options are Incorrect:** * **Option A:** While melanocytes do follow these lines, the term specifically refers to the broader migration of all **ectodermal** precursors (including keratinocytes). * **Options C & D:** Mesodermal and endodermal migrations follow different developmental patterns (e.g., dermatomes or internal organ mapping) and do not manifest as the characteristic S, V, or whorled shapes seen in Blaschko-linear dermatoses. **Clinical Pearls for NEET-PG:** * **Morphology:** They appear as **'V' shapes** on the upper back, **'S' shapes** on the abdomen, **inverted 'U' shapes** on the chest, and **linear patterns** on the limbs. * **Key Conditions:** Diseases following Blaschko’s lines include **Incontinentia Pigmenti** (X-linked dominant), **Linear Epidermal Nevus**, **Lichen Striatus**, and **Hypomelanosis of Ito**. * **Distinction:** Do not confuse them with **Dermatomes** (which follow spinal nerve distribution) or **Langer’s lines** (lines of skin tension used for surgical incisions).

Q: Oral examination of a 57-year-old female reveals a white patch on the buccal mucosa that cannot be scraped off. She has no features suggestive of immunosuppression. What is the most likely diagnosis?

Leukoplakia. **Explanation:** The clinical presentation of a **white patch on the buccal mucosa that cannot be scraped off** in an immunocompetent patient is the classic definition of **Leukoplakia**. 1. **Why Leukoplakia is correct:** According to the WHO, leukoplakia is a clinical term for a white patch or plaque that cannot be characterized clinically or pathologically as any other disease. The key diagnostic feature is that it is **non-scrapable**, distinguishing it from pseudomembranous candidiasis. It is considered a **premalignant (potentially malignant) condition**, often associated with tobacco use or chronic irritation. 2. **Why other options are incorrect:** * **Hairy Leukoplakia:** This is caused by the **Epstein-Barr Virus (EBV)** and typically presents as white, corrugated (shaggy) patches on the **lateral borders of the tongue**. It is almost exclusively seen in **immunocompromised** patients (e.g., HIV/AIDS). * **Erythroplakia:** This presents as a **fiery red patch** that cannot be characterized as any other condition. While it has a much higher risk of malignant transformation than leukoplakia, it does not present as a white patch. * **Thrush (Oral Candidiasis):** This presents as creamy white "curd-like" patches. Unlike leukoplakia, these patches **can be easily scraped off** with a tongue depressor, often leaving an erythematous, bleeding base. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site:** Buccal mucosa and floor of the mouth. * **Malignant Transformation:** The "speckled" variety (Erythroleukoplakia) has a higher risk of turning into Squamous Cell Carcinoma (SCC) than the homogenous type. * **Biopsy Rule:** Any white patch persisting for more than 2-3 weeks after removing local irritants must be biopsied to rule out dysplasia or malignancy.

Q: Which of the following conditions is characterized by the finding shown below?

Sturge-Weber syndrome. ***Sturge-Weber syndrome*** - Characterized by a **port-wine stain (nevus flammeus)** typically in the **trigeminal nerve distribution** on the face, which is the pathognomonic dermatological finding. - Associated with **leptomeningeal angiomatosis**, **seizures**, and **glaucoma**, making the facial port-wine stain a key diagnostic marker. *Neurofibromatosis type 1* - Primary dermatological findings include **café-au-lait macules** (≥6 spots >5mm prepubertal, >15mm postpubertal) and **neurofibromas**. - Also presents with **axillary/inguinal freckling** and **Lisch nodules** in the iris, not port-wine stains. *Tuberous sclerosis* - Characterized by **ash-leaf spots** (hypopigmented macules), **shagreen patches**, and **facial angiofibromas** (adenoma sebaceum). - **Periungual fibromas** and **forehead plaques** are also typical, but port-wine stains are not associated with this condition. *Von Hippel-Lindau disease* - Primarily affects **internal organs** with **retinal angiomas**, **cerebellar hemangioblastomas**, and **renal cell carcinomas**. - Has **minimal cutaneous manifestations** and is not associated with facial port-wine stains or other distinctive skin findings.

Question 1

A 28-year-old male presented with a rash on his arms, legs, and face, along with painful ulceration of his lips and mouth, and fever. He developed acute sore throat and conjunctivitis, leading to a diagnosis of acute pharyngitis. Oral penicillin was prescribed. Which of the following can be used in the treatment of the patient's condition, EXCEPT?

Accepted Answer

Cyclophosphamide

Answer

IVIg

Answer

Cyclosporine

Answer

Etanercept

Question 2

All of the following perforating disorders are associated with chronic renal failure EXCEPT:

Accepted Answer

Calciphylaxis

Answer

Reactive perforating collagenosis

Answer

Elastosis perforans serpiginosa

Answer

Kyrle disease

Question 3

Keloid formation is not typically seen over which of the following areas?

Accepted Answer

Eyelids

Answer

Ear

Answer

Face

Answer

Neck

Question 4

All of the following are primary lesions of the skin except:

Accepted Answer

Scar

Answer

Nodule

Answer

Purpura

Answer

Wheal

Question 5

Necrotic keratinocytes are typically seen in which of the following conditions?

Accepted Answer

All of the above

Answer

Discoid lupus erythematosus

Answer

Graft versus host disease

Answer

Erythema multiforme

Question 6

The pustular, neutrophil-rich skin lesions that develop or worsen following intradermal trauma is called what?

Accepted Answer

Pathergy

Answer

Erythema nodosum

Answer

Koebner Phenomenon

Answer

Dermatitis herpetiformis

Question 7

What is the approximate number of bacteria per square centimeter of skin?

Accepted Answer

10^2 - 10^3

Answer

10^1 - 10^2

Answer

10^5 - 10^10

Answer

Greater than 10^7

Question 8

Blaschko's lines refers to lines of what developmental process?

Accepted Answer

Ectodermal cell migration

Answer

Melanocyte migration

Answer

Mesodermal cell migration

Answer

Endodermal cell migration

Question 9

Oral examination of a 57-year-old female reveals a white patch on the buccal mucosa that cannot be scraped off. She has no features suggestive of immunosuppression. What is the most likely diagnosis?

Accepted Answer

Leukoplakia

Answer

Hairy leukoplakia

Answer

Erythroplakia

Answer

Thrush

Question 10

Which of the following conditions is characterized by the finding shown below?

Accepted Answer

Sturge-Weber syndrome

Answer

Neurofibromatosis type 1

Answer

Tuberous sclerosis

Answer

Von Hippel-Lindau disease

Basic Dermatology — MCQs

Basic Dermatology — MCQs

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