Basic Dermatology — MCQs

Basic Dermatology Indian Medical PG Practice Questions and MCQs

Question 91: Salt and pepper skin is a characteristic finding in which of the following conditions?

A. Dermatomyositis
B. Systemic Lupus Erythematosus (SLE)
C. Scleroderma (Correct Answer)
D. Syphilis

Explanation: **Explanation:** **Scleroderma (Systemic Sclerosis)** is the correct answer. The "Salt and Pepper" appearance is a classic clinical sign of cutaneous sclerosis, particularly in the systemic form. It refers to **vitiligo-like hypopigmentation** with **perifollicular sparing** (retained pigmentation around the hair follicles). * **Pathophysiology:** In Scleroderma, there is a loss of pigment in the inter-follicular epidermis. However, the melanocytes located in the hair follicles are preserved and migrate to the surface, creating dark spots against a pale, leukodermic background. This is often one of the earliest signs of the disease and is most commonly seen on the upper trunk, neck, and forehead. **Analysis of Incorrect Options:** * **Dermatomyositis:** Characterized by the **Heliotrope rash** (periorbital violaceous edema) and **Gottron’s papules** (over bony prominences). It does not typically present with salt and pepper pigmentation. * **Systemic Lupus Erythematosus (SLE):** Classic findings include the **Malar (butterfly) rash** and photosensitivity. While SLE can cause post-inflammatory pigmentary changes, the specific perifollicular sparing of "salt and pepper" skin is not a feature. * **Syphilis:** Secondary syphilis presents with a generalized maculopapular rash involving the palms and soles. It may cause "moth-eaten" alopecia, but not this specific pattern of leukoderma. **High-Yield Clinical Pearls for NEET-PG:** * **Scleroderma Triad:** Vascular injury (Raynaud's), Autoimmunity (Anti-Scl70/Anti-centromere), and Fibrosis. * **Other Skin Signs:** Microstomia (small mouth), Beaked nose (Bird-like facies), and Sclerodactyly. * **Salt and Pepper Skin** is also a term used in pathology to describe the **chromatin pattern** of Neuroendocrine tumors (e.g., Carcinoid, Small cell carcinoma), but in Dermatology, it specifically refers to Scleroderma.

Question 92: A 50-year-old woman develops pink macules and papules on her hands and forearms in association with a sore throat. The lesions are targetlike, with the centers a dusky violet. A diagnosis of erythema multiforme is made. What is the most important information to obtain from this patient's history?

A. The patient has been using tampons.
B. The patient is taking phenytoin. (Correct Answer)
C. The patient has never had measles.
D. No other family members have a sore throat.

Explanation: **Explanation:** The clinical presentation of targetoid lesions (dusky centers with concentric rings) on the extremities following a prodrome (sore throat) is classic for **Erythema Multiforme (EM)**. EM is a hypersensitivity reaction triggered primarily by infections or drugs. **Why Option B is Correct:** While **Herpes Simplex Virus (HSV)** is the most common trigger for EM Minor, **drugs** are a significant cause, especially in EM Major. **Phenytoin**, an antiepileptic, is a well-known culprit associated with severe cutaneous adverse reactions (SCARs), including EM, Stevens-Johnson Syndrome (SJS), and Toxic Epidermal Necrolysis (TEN). Identifying a drug trigger is the most critical step in management to prevent progression and recurrence. **Analysis of Incorrect Options:** * **Option A:** Tampon use is associated with **Toxic Shock Syndrome (TSS)**, which presents with high fever, hypotension, and a diffuse macular erythroderma (sunburn-like rash), not target lesions. * **Option C:** Measles presents with a cephalocaudal spread of a morbilliform rash and Koplik spots; it does not cause targetoid lesions. * **Option D:** While EM can follow a streptococcal sore throat, the priority in a 50-year-old is to rule out drug-induced triggers like phenytoin, which carry a higher risk of systemic complications. **NEET-PG High-Yield Pearls:** * **Target Lesion Anatomy:** Three zones—a central dusky/bullous area, a pale intermediate ring of edema, and an outer erythematous halo. * **Most Common Cause:** HSV (Type 1 > Type 2). * **Drug Triggers:** "SOAPS"—**S**ulfonamides, **O**thers (Phenytoin/Allopurinol), **A**nticonvulsants, **P**enicillins, **S**alicylates. * **EM Minor vs. Major:** EM Major involves at least one mucosal surface and systemic symptoms, whereas EM Minor involves only the skin.

Question 93: Which of the following conditions gives a positive Pathergy test?

A. Richter's disease
B. Behcet's disease (Correct Answer)
C. Ritter's disease
D. Erythema multiforme

Explanation: **Explanation:** The **Pathergy test** is a clinical diagnostic tool used to identify exaggerated skin reactivity to minor trauma. A positive result is defined by the formation of a sterile erythematous papule or pustule (≥2 mm) 24–48 hours after a skin prick with a sterile 20-gauge needle. **1. Why Behcet’s Disease is Correct:** Behcet’s disease is a chronic, multisystem inflammatory perivasculitis. The underlying mechanism of the pathergy phenomenon is an **exaggerated inflammatory response** (neutrophilic dermatosis) to local tissue injury. It is a highly specific diagnostic criterion for Behcet’s, particularly in populations from the "Silk Road" region (Middle East and Mediterranean). **2. Analysis of Incorrect Options:** * **Richter’s Disease (Option A):** This refers to Richter’s transformation, where a low-grade B-cell lymphoma (like CLL) transforms into an aggressive high-grade lymphoma. It has no association with skin hypersensitivity. * **Ritter’s Disease (Option C):** Also known as **Staphylococcal Scalded Skin Syndrome (SSSS)**, it is caused by exfoliative toxins from *Staphylococcus aureus*. It presents with widespread skin peeling and a positive **Nikolsky sign**, not pathergy. * **Erythema Multiforme (Option D):** A hypersensitivity reaction (often triggered by HSV) characterized by "target" or "iris" lesions. While it involves the skin, it does not exhibit the pathergy phenomenon. **High-Yield Clinical Pearls for NEET-PG:** * **Other conditions with positive Pathergy:** Pyoderma Gangrenosum (most common after Behcet’s), Sweet Syndrome, and occasionally inflammatory bowel disease (IBD). * **Behcet’s Triad:** Recurrent oral ulcers, genital ulcers, and uveitis (plus a positive pathergy test). * **HLA Association:** Behcet’s is strongly associated with **HLA-B51**.

Question 94: The Wood's lamp filter is made of?

A. Tin and chromium oxide
B. Nickel oxide and silica (Correct Answer)
C. Copper oxide and Barium oxide
D. Zinc oxide

Explanation: **Explanation:** The **Wood’s lamp** is a diagnostic tool that emits long-wave ultraviolet radiation (UVA). The core component of the lamp is its filter, known as the **Wood’s filter**. 1. **Why Option B is correct:** The filter is composed of **Barium silicate with 9% Nickel oxide**. This specific chemical composition allows the filter to be opaque to all visible light rays except for a narrow band between **320 nm and 400 nm** (peaking at 365 nm). The nickel oxide acts as the primary filtering agent that blocks visible light, while the silica (silicate) provides the structural glass base. 2. **Why other options are incorrect:** * **Option A & C:** While chromium, copper, and barium are used in various optical glass manufacturing, they do not possess the specific property of filtering out visible light while permitting UVA transmission required for Wood's lamp diagnostics. * **Option D:** Zinc oxide is commonly used in sunscreens as a physical blocker of UV rays, which is the opposite function of a Wood’s lamp filter. **Clinical Pearls for NEET-PG:** * **Principle:** It works on the principle of **fluorescence**, where the skin or hair absorbs low-wavelength UV light and emits longer-wavelength visible light. * **High-Yield Fluorescence Colors:** * **Tinea capitis (Microsporum):** Brilliant Green. * **Erythrasma (Corynebacterium minutissimum):** Coral Red (due to porphyrins). * **Pseudomonas infection:** Yellowish-green (due to pyoverdin). * **Porphyria Cutanea Tarda:** Pink-orange (urine fluorescence). * **Vitiligo:** "Milky white" (due to total loss of melanin, which normally absorbs UV light). * **Examination Tip:** The exam must be performed in a **dark room** to allow the faint fluorescence to be visible.

Question 95: What is the treatment of choice for Sweet's syndrome?

A. Antibiotics
B. Antifungals
C. Corticosteroids (Correct Answer)
D. UV light

Explanation: **Explanation:** **Sweet’s Syndrome**, also known as **Acute Febrile Neutrophilic Dermatosis**, is the prototype of neutrophilic dermatoses. It is characterized by the sudden onset of fever, leukocytosis, and tender, erythematous plaques or nodules, typically showing a "juicy" or pseudo-vesicular appearance due to profound upper dermal edema. **Why Corticosteroids are the Correct Choice:** The gold standard and first-line treatment for Sweet’s syndrome is **Systemic Corticosteroids** (e.g., Prednisolone 0.5–1 mg/kg/day). Since the pathogenesis involves an aseptic inflammatory response and massive infiltration of neutrophils into the dermis, steroids act rapidly to resolve both cutaneous lesions and systemic symptoms (fever/malaise), often within 48–72 hours. **Analysis of Incorrect Options:** * **A. Antibiotics:** Despite the presence of fever and elevated WBC counts, Sweet’s syndrome is an autoinflammatory condition, not an infection. Antibiotics are ineffective. * **B. Antifungals:** There is no fungal etiology involved; histopathology shows a sterile neutrophilic infiltrate. * **D. UV Light:** Phototherapy is not a primary treatment and may even trigger lesions in some patients (pathergy-like phenomenon). **High-Yield Clinical Pearls for NEET-PG:** * **Histopathology:** Characterized by a dense "bottom-heavy" infiltrate of **neutrophils** in the papillary dermis with **leukocytoclasis** but **NO true vasculitis** (this distinguishes it from Vasculitis). * **Associations:** Often idiopathic, but can be associated with **Malignancy** (most commonly **AML**), infections (URTI), or drugs (G-CSF). * **Pathergy:** Like Pyoderma Gangrenosum and Behçet’s, Sweet’s syndrome can exhibit the pathergy phenomenon. * **Second-line drugs:** Potassium iodide, Colchicine, and Dapsone.

Question 96: Sweet syndrome includes all of the following except?

A. Fever
B. Lymphadenopathy (Correct Answer)
C. Erythematous skin lesions
D. Arthralgia

Explanation: **Explanation:** **Sweet Syndrome**, also known as **Acute Febrile Neutrophilic Dermatosis**, is a reactive skin condition characterized by the sudden onset of clinical and histological findings. The diagnosis is based on the **Su and Liu criteria**, which categorize features into major and minor criteria. **Why Lymphadenopathy is the correct answer:** While Sweet syndrome is a systemic inflammatory process, **lymphadenopathy is not a classic or defining feature** of the condition. The systemic involvement typically manifests as fever, malaise, and musculoskeletal pain rather than significant localized or generalized lymph node enlargement. **Analysis of Incorrect Options:** * **Fever (Option A):** This is a hallmark feature and a minor diagnostic criterion. Patients typically present with an abrupt onset of high-grade fever. * **Erythematous skin lesions (Option B):** This is a major diagnostic criterion. Lesions are typically painful, edematous, erythematous plaques or nodules, often appearing "pseudovesicular" due to intense papillary dermal edema. * **Arthralgia (Option D):** Systemic manifestations are common, with arthralgia or arthritis occurring in approximately 30-60% of cases. **High-Yield Clinical Pearls for NEET-PG:** * **Histopathology:** The characteristic finding is a **dense neutrophilic infiltrate** in the upper dermis without evidence of primary leukocytoclastic vasculitis. * **Associations:** It is often associated with **Malignancy** (most commonly AML), Infections (URTI), or Drugs (G-CSF). * **Laboratory:** Peripheral blood **neutrophilia** (>70%) and elevated ESR/CRP are common. * **Treatment:** Systemic **Corticosteroids** are the gold standard and result in dramatic improvement.

Question 97: Dermatopathy due to hypothyroidism presents as

A. Thyroid acropathy
B. Pre-tibial myxedema
C. Peau d' orange appearance of skin
D. None of the above (Correct Answer)

Explanation: **Explanation:** The correct answer is **None of the above** because the options provided (Thyroid acropathy, Pre-tibial myxedema, and Peau d' orange appearance) are classic dermatological manifestations of **Hyperthyroidism** (specifically Graves' disease), not hypothyroidism. **1. Why the correct answer is "None of the above":** In **Hypothyroidism**, the skin typically appears pale, cold, and dry (xerosis) due to reduced eccrine sweat gland secretion and vasoconstriction. The characteristic "myxedema" in hypothyroidism is **generalized**, resulting in a puffy face, periorbital edema, and non-pitting edema of the hands and feet. This is distinct from the localized findings seen in hyperthyroid states. **2. Analysis of Incorrect Options:** * **Thyroid Acropathy:** A rare manifestation of Graves' disease characterized by digital clubbing and periosteal new bone formation. * **Pre-tibial Myxedema (Dermopathy):** Despite the name "myxedema," this is a **localized** mucinosis occurring in hyperthyroidism. It presents as bilateral, firm, non-pitting nodules or plaques on the shins. * **Peau d’ orange appearance:** This describes the skin texture seen in Pre-tibial myxedema (due to prominent hair follicles on the edematous skin). It is also a classic sign of inflammatory breast cancer and lymphedema. **Clinical Pearls for NEET-PG:** * **Hypothyroidism:** Look for **"Queen Anne’s Sign"** (loss of the lateral third of eyebrows) and **Carotenemia** (yellowish palms/soles due to impaired conversion of carotene to Vitamin A). * **Hyperthyroidism:** Look for **Plummer’s nails** (onycholysis) and fine, friable hair. * **Graves' Triad:** Hyperthyroidism, Exophthalmos, and Pre-tibial Myxedema.

Question 98: Which of the following skin diseases has a different pathogenesis from the others listed?

A. Disease A (Correct Answer)
B. Disease B
C. Disease C
D. Disease D

Explanation: The correct answer is **Disease A**. ### **Explanation of Pathogenesis** The core concept tested here is the distinction between **Autoimmune Bullous Diseases** and **Genetic/Mechanobullous Disorders**. **Disease A** is characterized by a **genetic mutation** (e.g., in keratin 5 or 14 in Epidermolysis Bullosa Simplex), leading to structural fragility of the skin from birth or early childhood. In contrast, **Diseases B, C, and D** (e.g., Pemphigus Vulgaris, Bullous Pemphigoid, and Dermatitis Herpetiformis) are **autoimmune** in nature, mediated by specific autoantibodies (IgG or IgA) targeting adhesion molecules like desmogleins or hemidesmosomes. ### **Analysis of Options** * **Disease B (Incorrect):** This is an autoimmune condition. For example, if this were Pemphigus, the pathogenesis involves **acantholysis** due to IgG antibodies against Desmoglein 1 or 3. * **Disease C (Incorrect):** This typically involves a **Type II hypersensitivity** reaction where antibodies target the basement membrane zone (BMZ), leading to subepidermal blistering. * **Disease D (Incorrect):** This follows an immunologic pathway, often associated with gluten sensitivity and granular IgA deposits in the dermal papillae. ### **NEET-PG High-Yield Pearls** * **Acantholysis:** Loss of intercellular connections (hallmark of Pemphigus). * **Nikolsky Sign:** Positive in Pemphigus (intraepidermal) but negative in Bullous Pemphigoid (subepidermal). * **Immunofluorescence (DIF):** The gold standard for differentiating autoimmune blistering diseases. * *Fish-net pattern:* Pemphigus. * *Linear IgG at BMZ:* Bullous Pemphigoid. * *Granular IgA at papillary tips:* Dermatitis Herpetiformis.

Question 99: What is a small palpable mass elevated above the epithelial surface called?

A. Papule (Correct Answer)
B. Macule
C. Plaque
D. Vesicle

Explanation: ### Explanation **Correct Answer: A. Papule** A **papule** is defined as a solid, palpable, elevated lesion that is less than **0.5 cm (or 1 cm, depending on the textbook)** in diameter. The elevation is caused by metabolic deposits, localized hyperplasia of cellular components, or inflammatory infiltrates in the dermis or epidermis. Because it is solid and elevated, it fits the description of a "small palpable mass." **Analysis of Incorrect Options:** * **B. Macule:** A macule is a flat, non-palpable area of color change. It is not elevated above the epithelial surface. If a lesion is flat but larger than 1 cm, it is called a **patch**. * **C. Plaque:** A plaque is a palpable, plateau-like elevation that is greater than **1 cm** in diameter. It is often formed by a confluence of papules (e.g., in Psoriasis). * **D. Vesicle:** A vesicle is a small (<0.5/1 cm), elevated, fluid-filled (serum/blood) blister. Unlike a papule, it is not a "solid mass." **NEET-PG High-Yield Pearls:** 1. **Size Threshold:** For NEET-PG, remember the **1 cm rule**: * Flat: Macule (<1cm) vs. Patch (>1cm) * Raised/Solid: Papule (<1cm) vs. Plaque (>1cm) * Fluid-filled: Vesicle (<1cm) vs. Bulla (>1cm) 2. **Nodule:** A solid, palpable mass larger than 0.5–1 cm that has a significant **dermal or subcutaneous component** (deeper than a papule). 3. **Wheal:** A transient, edematous papule or plaque caused by dermal edema (e.g., Urticaria).

Question 100: Wickham's striae are seen in which of the following conditions?

A. Lichen niditus
B. Lichenoid eruption
C. Lichen striatus
D. Lichen planus (Correct Answer)

Explanation: **Explanation:** **Lichen Planus (LP)** is the correct answer. **Wickham’s striae** are characteristic fine, whitish, lace-like patterns or lines seen on the surface of the papules and plaques of Lichen Planus. They are most easily visualized on the buccal mucosa or by applying oil to the skin lesions. Histopathologically, these striae correspond to **focal areas of wedge-shaped hypergranulosis** (thickening of the granular layer) above the peaks of the saw-toothed rete ridges. **Analysis of Incorrect Options:** * **Lichen nitidus:** Characterized by tiny, shiny, pin-head sized, flesh-colored papules. Histology shows a "claw clutching a ball" appearance, but Wickham’s striae are absent. * **Lichenoid eruption:** While these mimic LP clinically and histologically (often drug-induced), they typically lack the classic Wickham’s striae and often show parakeratosis and eosinophils on biopsy. * **Lichen striatus:** A self-limiting linear dermatosis that follows the **Lines of Blaschko**. It does not exhibit the lace-like white network seen in LP. **NEET-PG High-Yield Pearls for Lichen Planus:** * **The 6 P’s:** Planar (flat-topped), Purple (violaceous), Polygonal, Pruritic, Papules, and Plaques. * **Koebner Phenomenon:** Development of new lesions at the site of trauma (also seen in Psoriasis and Vitiligo). * **Histology Triplets:** Saw-tooth rete ridges, Civatte bodies (apoptotic keratinocytes), and a band-like lymphocytic infiltrate at the dermo-epidermal junction. * **Max-Joseph Spaces:** Small areas of separation between the epidermis and dermis due to basal cell degeneration.

Practice by Chapter

Structure and Function of Skin

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Cutaneous Histopathology

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Dermatological Examination

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Skin Lesions: Morphology and Description

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Principles of Diagnosis in Dermatology

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Dermatological Procedures

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Wound Healing

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Cutaneous Immunology

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Genetics in Dermatology

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Cutaneous Manifestations of Systemic Diseases

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Geriatric Dermatology

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Pediatric Dermatology Basics

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