Basic Dermatology Practice Questions

Q: Sebaceous cysts do not occur in which of the following locations?

Sole. **Explanation:** The correct answer is **Sole (Option D)**. **1. Why the Correct Answer is Right:** Sebaceous cysts (more accurately termed **Epidermal Inclusion Cysts**) are derived from the infundibulum of the hair follicle. Therefore, they can only occur in areas of the body that contain **pilosebaceous units** (hair follicles associated with sebaceous glands). The **palms and soles** are characterized by glabrous skin, which lacks hair follicles and sebaceous glands entirely. Consequently, a true sebaceous or epidermal cyst cannot develop in these locations. **2. Why the Incorrect Options are Wrong:** * **Scalp (Option A):** This is one of the most common sites for cysts. While most "sebaceous cysts" on the scalp are technically **pilar cysts** (trichilemmal cysts), epidermal cysts also occur frequently here due to the high density of hair follicles. * **Scrotum (Option B):** The scrotum is rich in sebaceous glands. It is a classic site for multiple sebaceous cysts, which may sometimes undergo calcification (Idiopathic Scrotal Calcinosis). * **Back (Option C):** The trunk and back are high-density areas for sebaceous glands and are among the most common clinical presentations for epidermal inclusion cysts. **3. Clinical Pearls for NEET-PG:** * **Punctum:** A key diagnostic feature of an epidermal cyst is the presence of a central pore or "punctum," which represents the opening of the follicle. * **Contents:** These cysts are filled with **keratin**, not sebum. They have a cheesy, foul-smelling material. * **Gardner Syndrome:** Multiple epidermal cysts (especially in unusual locations or at a young age) should raise suspicion for Gardner Syndrome (associated with familial adenomatous polyposis). * **Glabrous Skin:** Remember, palms and soles lack sebaceous glands and melanocytes (in the stratum basale), but have a high density of **eccrine sweat glands**.

Q: What is the most common site of Necrobiosis lipoidica diabeticorum?

Front of the leg. ### Explanation **Necrobiosis Lipoidica (NL)**, formerly known as Necrobiosis Lipoidica Diabeticorum, is a chronic granulomatous skin disorder. While it is strongly associated with diabetes mellitus (occurring in approximately 0.3% of diabetic patients), it can also occur in non-diabetic individuals. **Why "Front of the leg" is correct:** The most characteristic and common site for NL is the **pretibial area (shins)**, which corresponds to the **front of the leg**. The lesions typically present as well-demarcated, erythematous papules that evolve into yellowish-brown, atrophic, telangiectatic plaques with a "glazed" or "parchment-like" appearance. The predilection for the shins is thought to be due to relative poor vascularity and increased trauma in this area, leading to collagen degeneration (necrobiosis). **Why other options are incorrect:** * **Face and Neck:** These are extremely rare sites for NL. Lesions on the face or scalp are more likely to be Granuloma Annulare or Sarcoidosis, which are important differential diagnoses. * **Back of the leg:** While NL can occasionally involve the calves or ankles, the involvement is overwhelmingly bilateral and symmetrical on the anterior (front) surface of the lower extremities. **High-Yield Clinical Pearls for NEET-PG:** * **Pathology:** Characterized by "tiered" or "layered" granulomatous inflammation in the dermis (alternating layers of necrobiotic collagen and inflammatory cells). * **Clinical Sign:** The center of the plaque often becomes thin and atrophic, making it prone to **ulceration** following minor trauma (seen in 35% of cases). * **Diabetes Correlation:** The presence or severity of NL does **not** correlate with glycemic control; however, patients with NL have a higher incidence of diabetic nephropathy and retinopathy. * **Differential Diagnosis:** Granuloma Annulare (which lacks the atrophy and telangiectasia seen in NL).

Q: Ivory/milky-white fluorescence on Wood's Lamp Examination is seen in which of the following conditions?

Vitiligo. **Explanation:** **Wood’s Lamp Examination** is a high-yield diagnostic tool in dermatology that uses long-wave ultraviolet light (365 nm). The appearance of specific colors under this lamp helps differentiate various pigmentary and infectious disorders. **1. Why Vitiligo is the Correct Answer:** In **Vitiligo**, there is a complete absence of epidermal melanocytes. Melanin normally absorbs UV light; without it, the light penetrates deeper and is reflected by dermal collagen. This results in a sharp, bright **ivory-white or milky-white fluorescence**. Wood’s lamp is particularly useful in identifying subclinical patches in fair-skinned individuals and differentiating vitiligo from other hypopigmented disorders. **2. Analysis of Incorrect Options:** * **Pityriasis versicolor:** Caused by *Malassezia* species, it typically shows a **yellowish or golden-yellow** fluorescence. * **Tinea capitis:** Specifically types caused by *Microsporum* species (e.g., *M. audouinii*) show a **bright green or blue-green** fluorescence. Note: *Trichophyton tonsurans* (the most common cause) does not fluoresce. * **Erythrasma:** Caused by *Corynebacterium minutissimum*, it produces porphyrins that result in a characteristic **coral-red** fluorescence. **Clinical Pearls for NEET-PG:** * **Pseudomonas infection:** Shows **apple-green** fluorescence (due to pyoverdin). * **Porphyria Cutanea Tarda:** Urine shows **pink-orange/red** fluorescence. * **Melasma:** Wood’s lamp helps determine depth; **epidermal** type becomes more prominent, while **dermal** type becomes less apparent under the lamp. * **Ash-leaf spots (Tuberous Sclerosis):** Show a dull white (hypopigmented) appearance, but not the brilliant "milky" glow of vitiligo.

Q: Which of the following conditions is NOT associated with pancreatic panniculitis?

Pancreatic mucinous cyst. ### Explanation **Pancreatic panniculitis** (also known as enzymatic fat necrosis) is a rare skin manifestation occurring in approximately 2–3% of patients with pancreatic disease. It is characterized by painful, erythematous nodules, typically on the lower extremities, which may ulcerate and discharge an oily substance. **Why Option D is correct:** Pancreatic mucinous cysts (such as Mucinous Cystadenomas) are typically localized, slow-growing neoplastic lesions. They generally do not cause a massive systemic release of pancreatic enzymes into the circulation. Pancreatic panniculitis requires **high levels of circulating amylase and lipase**, which hydrolyze subcutaneous fat, leading to "ghost cells" (anucleated adipocytes with shadowy cell walls) on histology. **Why the other options are incorrect:** * **Acute and Chronic Pancreatitis (Options B & C):** These are the most common causes. Inflammation leads to the leakage of acinar enzymes into the portal and systemic circulation, triggering distal fat necrosis. * **Pancreatic Cancer (Option A):** Specifically, **Acinar Cell Carcinoma** is strongly associated with pancreatic panniculitis (Schmid’s triad: panniculitis, polyarthritis, and eosinophilia). The tumor cells actively secrete lipase, leading to widespread fat necrosis. ### High-Yield Clinical Pearls for NEET-PG: * **Histology Keyword:** Look for **"Ghost Cells"** (pathognomonic)—adipocytes that have lost their nuclei but retain their cellular outlines due to saponification. * **Schmid’s Triad:** Pancreatic panniculitis + Polyarthritis + Eosinophilia (associated with a poor prognosis in pancreatic malignancy). * **Clinical Presentation:** Often precedes the diagnosis of the underlying pancreatic pathology by several weeks. * **Distribution:** Most common on the shins, mimicking Erythema Nodosum, but distinguished by the "oily" discharge.

Q: Which one of the following conditions is associated with palpable purpura?

Acute meningococcemia. **Explanation:** The hallmark of **palpable purpura** is **leukocytoclastic vasculitis (LCV)**. Unlike non-palpable purpura, which results from simple extravasation of blood into the skin, palpable purpura indicates inflammatory damage to the vessel wall, leading to both hemorrhage and inflammatory edema/infiltration. **Why Acute Meningococcemia is Correct:** Acute meningococcemia (caused by *Neisseria meningitidis*) triggers an intense inflammatory response and septic vasculitis. The bacteria damage the vascular endothelium, leading to fibrin thrombi and vessel wall inflammation. This manifests clinically as petechiae that rapidly evolve into **palpable purpura** and eventually purpura fulminans. **Analysis of Incorrect Options:** * **ITP (Immune Thrombocytopenic Purpura):** This is caused by low platelet counts. Since the vessel walls remain intact and there is no inflammation, the resulting purpura is **non-palpable (flat)**. * **Scurvy:** Vitamin C deficiency leads to defective collagen synthesis, resulting in fragile capillary walls. This causes **non-palpable** perifollicular hemorrhages and "corkscrew hairs." * **DIC (Disseminated Intravascular Coagulation):** While DIC involves widespread clotting and bleeding, the primary mechanism is a consumptive coagulopathy. The skin lesions are typically large, **flat** ecchymoses or purpura fulminans without the primary inflammatory component of vasculitis. **NEET-PG High-Yield Pearls:** * **Palpable Purpura = Vasculitis** until proven otherwise. * The most common cause of palpable purpura in children is **Henoch-Schönlein Purpura (HSP)**. * **Non-palpable purpura** is usually due to thrombocytopenia, clotting factor deficiencies, or vascular fragility (e.g., senile purpura, steroids). * In meningococcemia, the presence of palpable purpura is a medical emergency requiring immediate intravenous antibiotics.

Q: A man, after consuming seafood, develops rashes. What is the likely immunological mechanism?

IgE mediated. **Explanation:** The clinical presentation of rashes immediately following the consumption of a specific food (seafood) is a classic manifestation of a **Type I Hypersensitivity Reaction**. [1] **Why IgE-mediated is correct:** Seafood (crustaceans/fish) contains specific proteins that act as allergens. Upon first exposure, the body produces **IgE antibodies** that bind to the surface of mast cells and basophils. [1] On subsequent exposure, the allergen cross-links these IgE antibodies, triggering **degranulation**. [1] This releases potent inflammatory mediators, primarily **histamine**, which causes vasodilation and increased capillary permeability, leading to the development of urticaria (rashes) or even anaphylaxis. [1] **Why other options are incorrect:** * **Complement activation:** This is characteristic of **Type II** (Cytotoxic) or **Type III** (Immune-complex) hypersensitivity. While complement can be involved in chronic inflammatory states, it is not the primary driver of acute food-induced allergic rashes. * **Cell-mediated:** This refers to **Type IV** (Delayed-type) hypersensitivity, mediated by T-cells rather than antibodies. These reactions typically take 48–72 hours to manifest (e.g., Contact Dermatitis or the Mantoux test) and do not present as immediate rashes after ingestion. **High-Yield Clinical Pearls for NEET-PG:** * **Type I Hypersensitivity:** Remember the mnemonic **"A"** for **A**naphylaxis, **A**topy, and **A**sthma. * **Key Mediator:** Histamine is the primary pre-formed mediator [1]; Leukotrienes (C4, D4, E4) are secondary mediators. * **Seafood Allergy:** This is one of the most common triggers for adult-onset food allergies and is often lifelong. * **Treatment:** For simple rashes, H1-antihistamines are used; for systemic involvement (anaphylaxis), the drug of choice is **Intramuscular Adrenaline (1:1000)**.

Q: Which of the following is an oral manifestation of lichen planus?

White radiating lines on the buccal mucosa. **Explanation:** **Lichen Planus (LP)** is a chronic inflammatory condition affecting the skin and mucous membranes. The correct answer is **White radiating lines on the buccal mucosa**, which are clinically known as **Wickham’s striae**. In the oral cavity, LP most commonly presents as a reticular pattern of white, lacy, interconnected lines, typically involving the posterior buccal mucosa bilaterally. This occurs due to the destruction of the basal cell layer by T-cells, leading to hyperkeratosis and a characteristic "saw-tooth" appearance of the rete ridges on histology. **Analysis of Incorrect Options:** * **Dentinogenesis imperfecta:** This is a genetic disorder of tooth development (dentin formation) often associated with Osteogenesis Imperfecta; it is not related to inflammatory dermatoses. * **Fordyce spots:** These are ectopic sebaceous glands appearing as small, yellowish-white papules on the oral mucosa. They are a normal anatomical variant, not a pathology. * **White, chalky enamel surface:** This is a classic sign of early **Dental Caries** or **Fluorosis**, representing demineralization or hypomineralization of the enamel. **High-Yield Clinical Pearls for NEET-PG:** * **The 6 P’s of LP:** Planar, Purple, Polygonal, Pruritic, Papules, and Plaques. * **Koebner Phenomenon:** New lesions appearing at the site of trauma (also seen in Psoriasis and Vitiligo). * **Variants:** Oral LP can be reticular (most common), erosive (painful/premalignant), or bullous. * **Histology:** Look for "Saw-tooth" rete ridges, Civatte bodies (apoptotic keratinocytes), and a band-like lymphocytic infiltrate at the dermo-epidermal junction.

Q: Peripheral 'Collarette of scales' is a characteristic feature of which dermatological condition?

Psoriasis rosea. **Explanation:** The correct answer is **Pityriasis rosea** (Note: The option provided as "Psoriasis rosea" is a common nomenclature error in some question banks; the medical term is Pityriasis rosea). **1. Why Pityriasis Rosea is Correct:** The **"Collarette of scales"** is the pathognomonic clinical feature of Pityriasis Rosea (PR). It refers to a thin, fine rim of scales attached at the periphery with a free central edge, typically seen within the oval, salmon-colored erythematous plaques. This occurs because the scale peels outward from the center. PR often begins with a single, large **"Herald Patch"** followed by a generalized eruption in a **"Christmas Tree"** or "Fir Tree" distribution along the skin tension lines (Langer’s lines). **2. Why Other Options are Incorrect:** * **Pityriasis versicolor:** Characterized by "furfuraceous" (fine, powdery) scales that become prominent upon scratching (**Besnier’s sign** or the Stroke sign). * **Lichen planus:** Characterized by the 6 P's (Planar, Purple, Polygonal, Pruritic, Papules, and Plaques) and **Wickham striae** (whitish reticular lines), not peripheral scaling. * **Pityriasis rubra pilaris (PRP):** Known for follicular papules on an erythematous base, "islands of sparing," and orange-red palmoplantar keratoderma. **High-Yield Clinical Pearls for NEET-PG:** * **Etiology:** Associated with Human Herpesvirus 6 and 7 (**HHV-6/7**). * **Herald Patch:** The initial lesion, usually 2–10 cm, appearing days to weeks before the secondary eruption. * **Distribution:** Follows Langer’s lines on the trunk. * **Treatment:** Self-limiting (6–8 weeks); symptomatic relief with antihistamines or topical steroids. Narrowband UVB can be used in severe cases.

Q: Mutation in Keratin 1 and 10 are associated with which condition?

Epidermolytic hyperkeratosis. ### Explanation **Correct Answer: B. Epidermolytic hyperkeratosis (EHK)** Keratins are intermediate filament proteins that provide structural integrity to epithelial cells. They are expressed in specific pairs depending on the layer of the skin. **Keratin 1 (K1) and Keratin 10 (K10)** are the primary keratins of the **suprabasal layers** (stratum spinosum and granulosum). Mutation in K1 or K10 leads to **Epidermolytic Hyperkeratosis** (also known as Bullous Congenital Ichthyosiform Erythroderma). The defect causes the keratin filaments to clump, weakening the structural support of the cells. This results in intraepidermal blistering (due to cytolysis) and subsequent massive compensatory hyperkeratosis. **Analysis of Incorrect Options:** * **A. Epidermolysis bullosa simplex (EBS):** This is caused by mutations in **K5 and K14**, which are expressed in the **basal layer** of the epidermis. * **C. Epidermolytic palmoplantar keratoderma (EPPK):** This condition (Vorner type) is specifically associated with mutations in **K9**, which is uniquely expressed in the palms and soles. * **D. Meesmann epithelial corneal dystrophy:** This is caused by mutations in **K3 and K12**, which are specific to the corneal epithelium. **High-Yield Clinical Pearls for NEET-PG:** * **K5/K14:** Basal layer (EBS). * **K1/K10:** Suprabasal layers (EHK/BCIE). * **K6/K16:** Nail bed and palmoplantar skin (Pachyonychia Congenita Type 1). * **K1/K9:** Palmoplantar Keratoderma. * **Histopathology of EHK:** Characterized by "granular degeneration"—vacuolization of the keratinocytes in the stratum spinosum and granulosum with large, irregular keratohyalin granules.

Q: A 16-year-old boy presented with asymptomatic, multiple, erythematous, annular lesions with a collarette of scales at the periphery of the lesions present on the trunk. What is the most likely diagnosis?

Pityriasis rosea. ### Explanation **Correct Option: C. Pityriasis rosea** The clinical presentation of **annular, erythematous lesions** with a characteristic **collarette of scales** (scales attached at the periphery with the free edge pointing inwards) is the hallmark of **Pityriasis rosea (PR)**. PR typically affects adolescents and young adults. It often begins with a single, larger "Herald Patch," followed by a generalized eruption on the trunk and proximal limbs. The lesions follow the lines of cleavage (Langer’s lines), creating the classic **"Christmas Tree" appearance**. It is thought to be associated with Human Herpesvirus 6 and 7 (HHV-6/7). **Why other options are incorrect:** * **A. Pityriasis versicolor:** Presents as hypo- or hyperpigmented macules with fine, "branny" (furfuraceous) scales. It lacks the annular configuration and the specific inward-pointing collarette of scales. * **B. Pityriasis alba:** Characterized by ill-defined, hypopigmented patches with very fine scaling, usually on the face of children. It is considered a manifestation of atopic dermatitis and does not present with erythematous annular lesions. * **D. Pityriasis rubra pilaris (PRP):** Presents with follicular papules on an erythematous base, "islands of sparing" (normal skin within affected areas), and orange-red palmoplantar keratoderma. It does not feature the peripheral collarette of scales. **High-Yield Clinical Pearls for NEET-PG:** * **Herald Patch:** The initial, largest lesion (2–6 cm) seen in 50-90% of PR cases. * **Collarette of Scales:** Scales are attached peripherally and trail toward the center. * **Hanging Curtain Sign:** When the skin is pinched, the scales fold like a curtain (specific to PR). * **Treatment:** Usually self-limiting (6–8 weeks). Reassurance is key; topical steroids or antihistamines are used for pruritus.

Question 1

Sebaceous cysts do not occur in which of the following locations?

Accepted Answer

Sole

Answer

Scalp

Answer

Scrotum

Answer

Back

Question 2

What is the most common site of Necrobiosis lipoidica diabeticorum?

Accepted Answer

Front of the leg

Answer

Face

Answer

Neck

Answer

Back of the leg

Question 3

Ivory/milky-white fluorescence on Wood's Lamp Examination is seen in which of the following conditions?

Accepted Answer

Vitiligo

Answer

Pityriasis versicolor

Answer

Tinea capitis

Answer

Erythrasma

Question 4

Which of the following conditions is NOT associated with pancreatic panniculitis?

Accepted Answer

Pancreatic mucinous cyst

Answer

Pancreas cancer

Answer

Chronic pancreatitis

Answer

Acute pancreatitis

Question 5

Which one of the following conditions is associated with palpable purpura?

Accepted Answer

Acute meningococcemia

Answer

Immune Thrombocytopenic Purpura (ITP)

Answer

Scurvy

Answer

Disseminated Intravascular Coagulation (DIC)

Question 6

A man, after consuming seafood, develops rashes. What is the likely immunological mechanism?

Accepted Answer

IgE mediated

Answer

Complement activation

Answer

Cell mediated

Answer

None of the above

Question 7

Which of the following is an oral manifestation of lichen planus?

Accepted Answer

White radiating lines on the buccal mucosa

Answer

Dentinogenesis imperfecta

Answer

Fordyce spots

Answer

White, chalky enamel surface

Question 8

Peripheral 'Collarette of scales' is a characteristic feature of which dermatological condition?

Accepted Answer

Psoriasis rosea

Answer

Psoriasis versicolor

Answer

Lichen planus

Answer

Pityriasis rubra pilaris

Question 9

Mutation in Keratin 1 and 10 are associated with which condition?

Accepted Answer

Epidermolytic hyperkeratosis

Answer

Epidermolysis bullosa simplex

Answer

Epidermolytic palmoplantar keratoderma

Answer

Meesmann epithelial corneal dystrophy

Question 10

A 16-year-old boy presented with asymptomatic, multiple, erythematous, annular lesions with a collarette of scales at the periphery of the lesions present on the trunk. What is the most likely diagnosis?

Accepted Answer

Pityriasis rosea

Answer

Pityriasis versicolor

Answer

Pityriasis alba

Answer

Pityriasis rubra pilaris

Basic Dermatology — MCQs

Basic Dermatology — MCQs

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