Basic Dermatology Practice Questions

Q: A patient with a history of smoking, essential hypertension, hypercholesterolemia, and hyperuricemia presents for follow-up. Oral examination findings from three visits are available. What is the most likely diagnosis of the tongue involvement?

Geographic tongue. ***Geographic tongue*** - Characterized by **migratory erythematous patches** with **white or yellow borders** that change location and appearance across multiple visits, explaining the varying oral examination findings. - Also known as **benign migratory glossitis**, it presents as **depapillated areas** on the tongue dorsum that create a map-like appearance and is often asymptomatic. *Oral candidiasis* - Presents as **white plaques** that can be **wiped off** easily, leaving an erythematous base underneath. - Typically associated with **immunocompromised states**, antibiotic use, or diabetes, and would show consistent findings rather than changing patterns across visits. *Lichen planus* - Characterized by **white lacy streaks** (Wickham's striae) or **reticular patterns** that remain relatively stable over time. - Often involves **bilateral buccal mucosa** and may cause **erosive lesions** with burning sensation, unlike the migrating nature seen in this case. *Oral hairy leukoplakia* - Presents as **white, corrugated patches** on the **lateral borders** of the tongue that cannot be wiped off. - Strongly associated with **HIV infection** and **Epstein-Barr virus**, showing consistent appearance rather than the changing pattern described across multiple visits.

Q: Leg ulcers are typically associated with which of the following conditions, EXCEPT?

Psoriasis. **Explanation:** The correct answer is **Psoriasis**. Leg ulcers are defined as a loss of epidermal and dermal integrity below the knee. While psoriasis is a chronic inflammatory dermatosis characterized by well-demarcated erythematous plaques with silvery scales, it **does not typically present with ulceration**. In psoriasis, the skin barrier is thickened (hyperkeratosis/acanthosis) rather than lost. **Analysis of Options:** * **Tuberculosis (TB):** Cutaneous TB, specifically **Erythema Induratum (Bazin’s disease)**, typically presents as chronic, recurring nodules on the calves that frequently undergo ulceration. **Lupus Vulgaris** can also lead to ulcerated plaques. * **Syphilis:** Late benign syphilis (Tertiary stage) is characterized by **Gummas**. These are granulomatous lesions that often break down to form painless, "punched-out" ulcers, commonly found on the pretibial aspect of the legs. * **Anemia:** Chronic hemolytic anemias, most notably **Sickle Cell Anemia** and Thalassemia, are well-known causes of leg ulcers. The pathophysiology involves microvascular occlusion, tissue hypoxia, and reduced nitric oxide bioavailability. **Clinical Pearls for NEET-PG:** * **Most common cause of leg ulcers:** Venous insufficiency (70%), followed by arterial insufficiency. * **Punched-out ulcers:** Classic description for Syphilitic gumma and Arterial (Ischemic) ulcers. * **Pyoderma Gangrenosum:** A rapidly spreading, painful ulcer with a "violaceous undermined border," often associated with IBD or Rheumatoid Arthritis. * **Marjolin’s Ulcer:** A Squamous Cell Carcinoma arising in a site of chronic inflammation or a long-standing burn scar.

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

365 nm. **Explanation:** A **Wood’s lamp** (also known as black light) is a diagnostic tool that emits long-wave Ultraviolet A (UVA) radiation. It utilizes a high-pressure mercury arc lamp equipped with 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 **365 nm**. * **Why 365 nm is correct:** This wavelength falls within the UVA spectrum (320–400 nm). When this light strikes certain skin structures or pathogens, they absorb the energy and re-emit it as visible light (fluorescence), which is essential for diagnosing fungal, bacterial, and pigmentary disorders. * **Why other options are incorrect:** * **400 nm:** This marks the transition point between UVA and visible violet light; it is too long to be the specific peak of a Wood's lamp. * **320 nm:** This is the boundary between UVB and UVA. While within the filter's range, it is not the peak emission wavelength. * **200 nm:** This falls under UVC (germicidal) radiation, which is harmful to the skin and eyes and is filtered out by the Wood's lamp. **High-Yield Clinical Pearls for NEET-PG:** 1. **Tinea Capitis:** *Microsporum* species show **Brilliant Green** fluorescence. (*Trichophyton schoenleinii* shows dull green). 2. **Erythrasma:** Caused by *Corynebacterium minutissimum*; shows **Coral Red** fluorescence due to porphyrins. 3. **Pseudomonas:** Shows **Yellow-Green** fluorescence (Pyoverdin). 4. **Porphyria Cutanea Tarda:** Urine shows **Pink-Orange** fluorescence. 5. **Pigmentary changes:** Wood’s lamp enhances the contrast in **Vitiligo** (depigmentation) but does not enhance **Dermal melanosis**.

Q: A child presents with recurrent mouth ulcers that typically begin as a round, yellowish, elevated spot surrounded by a red halo and heal within 7-10 days. What is the most likely diagnosis?

Aphthous ulcers. **Explanation:** The clinical presentation described is classic for **Aphthous Ulcers** (Recurrent Aphthous Stomatitis). These are the most common cause of recurrent oral ulceration. The hallmark is a painful, shallow, round-to-oval ulcer with a **yellowish-gray pseudomembranous center** and a prominent **erythematous (red) halo**. They typically heal spontaneously within 7–14 days without scarring (minor type). **Analysis of Options:** * **Aphthous Ulcers (Correct):** The description of a yellowish spot with a red halo and a 7–10 day healing cycle is pathognomonic. They are non-contagious and often triggered by stress, trauma, or nutritional deficiencies (B12, Iron, Folate). * **Gingivitis:** This refers to inflammation of the gums characterized by redness, swelling, and bleeding, rather than discrete, self-healing ulcers. * **Malignancy:** Squamous cell carcinoma usually presents as a chronic, non-healing, indurated ulcer with rolled-out edges, often in older patients with risk factors (tobacco/alcohol). It would not heal in 10 days. * **Herpetic Ulcer:** Primary herpetic gingivostomatitis usually presents with multiple small vesicles that rupture into ulcers, often accompanied by high fever, lymphadenopathy, and involvement of the keratinized mucosa (hard palate/gingiva), unlike aphthous ulcers which prefer non-keratinized mucosa. **NEET-PG High-Yield Pearls:** * **Site:** Aphthous ulcers occur on **non-keratinized mucosa** (buccal/labial mucosa, floor of mouth). * **Behçet’s Disease:** Always consider this if oral ulcers are associated with genital ulcers and uveitis (Triple Symptom Complex). * **Management:** Topical corticosteroids (e.g., Triamcinolone acetonide) and topical analgesics (Lidocaine) are first-line treatments.

Q: All of the following conditions are a differential diagnosis for Koebner Phenomenon, EXCEPT:

Pyoderma gangrenosum. ### Explanation The key to answering this question lies in distinguishing between the **Koebner Phenomenon** and **Pathergy**. **1. Why Pyoderma Gangrenosum (PG) is the correct answer:** Pyoderma gangrenosum is characterized by **Pathergy**, not the Koebner phenomenon. While both involve skin lesions developing at sites of trauma, they are pathophysiologically distinct. Pathergy refers to an exaggerated inflammatory response (often pustular or ulcerative) to minor trauma (e.g., a needle prick). In contrast, the Koebner phenomenon involves the appearance of new lesions of a *pre-existing* skin disease on previously healthy skin following trauma. **2. Why the other options are incorrect:** * **Lichen planus (A):** This is one of the "classic" examples of the Koebner phenomenon. Linear lichenoid papules often appear along scratch marks. * **Vitiligo (B):** Depigmented patches frequently develop at sites of friction or injury (e.g., elbows, waistline), representing a positive Koebner response. * **Leukocytoclastic vasculitis (D):** This is a recognized cause of the "Pseudo-Koebner" or true Koebner response, where palpable purpura develops in areas of pressure or trauma. **3. NEET-PG High-Yield Pearls:** * **True Koebner Phenomenon (Isomorphic response):** Psoriasis (most common), Lichen Planus, Vitiligo, Pityriasis Rubra Pilaris (PRP). * **Pseudo-Koebner Phenomenon:** Seen in infectious conditions where trauma inoculates the virus into the skin (e.g., **Molluscum contagiosum, Verruca plana**). * **Pathergy Positive Conditions:** Pyoderma Gangrenosum, **Behçet’s Disease**, and Sweet Syndrome. * **Reverse Koebner:** Disappearance of a lesion following trauma to the area.

Q: A 24-year-old male presents with a skin condition. What is the provisional diagnosis for this condition?

Erythema multiforme. ***Erythema multiforme*** - Characterized by **target/iris lesions** with a central dusky area surrounded by a pale ring and outer erythematous border, which is the classic presentation. - Commonly affects **young adults** and is often triggered by **HSV infections** or certain medications like **sulfonamides**. *Psoriasis* - Presents with **well-demarcated silvery-scaled plaques** typically on extensor surfaces like knees and elbows. - Lesions show **Koebner phenomenon** and **Auspitz sign** when scales are removed, not target-like morphology. *Lichen planus* - Characterized by **purple, polygonal, pruritic papules** with **Wickham's striae** on the surface. - Commonly affects **flexor surfaces** and mucous membranes, showing a different morphology than target lesions. *Lichen striatus* - Presents as a **linear band** of small, flesh-colored to pink papules following **Blaschko's lines**. - Typically occurs in **children** and shows a distinctive linear pattern, not circular target lesions.

Q: Crocodile skin or sauroderma is seen in which of the following conditions?

Ichthyosis vulgaris. **Explanation:** **Ichthyosis vulgaris** is the correct answer. The term "Ichthyosis" is derived from the Greek word *ichthys*, meaning fish. It is an autosomal dominant disorder caused by a mutation in the **filaggrin (FLG) gene**, which leads to defective keratinization and impaired skin barrier function. Clinically, it presents as diffuse, fine, polygonal scales that resemble **crocodile skin** or **fish scales** (sauroderma). These scales are most prominent on the extensors of the lower limbs, while the flexures (axilla, cubital fossa) are characteristically spared. **Analysis of Incorrect Options:** * **Toxic Epidermal Necrolysis (TEN):** This is a severe drug reaction characterized by widespread erythema and full-thickness epidermal detachment (sheeting off of skin), not scaling. It presents with a positive Nikolsky sign. * **Psoriasis:** Characterized by well-demarcated erythematous plaques with **silvery-white scales**. Key features include the Auspitz sign and Koebner phenomenon. * **Darier’s Disease:** An autosomal dominant acantholytic disorder presenting with greasy, brown, malodorous **keratotic papules** in seborrheic areas, rather than diffuse fish-like scaling. **Clinical Pearls for NEET-PG:** * **Hyperlinear palms:** A classic association with Ichthyosis vulgaris and Atopic Dermatitis. * **Sparing of flexures:** A key diagnostic feature distinguishing Ichthyosis vulgaris from X-linked recessive ichthyosis (which involves flexures and presents with "dirty" brown scales). * **Filaggrin mutation:** Also the most significant genetic risk factor for **Atopic Dermatitis**. * **Treatment:** Emollients and keratolytics (e.g., urea, lactic acid, or salicylic acid).

Question 1

A patient with a history of smoking, essential hypertension, hypercholesterolemia, and hyperuricemia presents for follow-up. Oral examination findings from three visits are available. What is the most likely diagnosis of the tongue involvement?

Accepted Answer

Geographic tongue

Answer

Oral candidiasis

Answer

Lichen planus

Answer

Oral hairy leukoplakia

Question 2

A 40-year-old diabetic patient presents with round lesions on the abdomen for 2 weeks. Histopathology shows a palisading granuloma. What is the diagnosis?

Accepted Answer

Granuloma annulare

Answer

Pemphigus erythematosus

Answer

Leprosy

Answer

Tinea

Question 3

Leg ulcers are typically associated with which of the following conditions, EXCEPT?

Accepted Answer

Psoriasis

Answer

Tuberculosis

Answer

Syphilis

Answer

Anemia

Question 4

Palpable purpura is seen in which of the following conditions?

Accepted Answer

Henoch-Schönlein Purpura

Answer

Idiopathic thrombocytopenic purpura (ITP)

Answer

Scurvy

Answer

Monoclonal cryoglobulinemia

Question 5

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

Accepted Answer

365 nm

Answer

400 nm

Answer

320 nm

Answer

200 nm

Question 6

A child presents with recurrent mouth ulcers that typically begin as a round, yellowish, elevated spot surrounded by a red halo and heal within 7-10 days. What is the most likely diagnosis?

Accepted Answer

Aphthous ulcers

Answer

Gingivitis

Answer

Malignancy

Answer

Herpetic ulcer

Question 7

All of the following conditions are a differential diagnosis for Koebner Phenomenon, EXCEPT:

Accepted Answer

Pyoderma gangrenosum

Answer

Lichen planus

Answer

Vitiligo

Answer

Leukocytoclastic vasculitis

Question 8

An 85-year-old male cigar smoker with no notable medical history presented with black discoloration and hairy appearance of the tongue, which had lasted several years. He denied using bismuth-containing compounds. What is the cause of this lesion on the tongue?

Accepted Answer

Lingua villosa nigra

Answer

Aspergillosis

Answer

Adrenal insufficiency

Answer

Pellagra

Question 9

A 24-year-old male presents with a skin condition. What is the provisional diagnosis for this condition?

Accepted Answer

Erythema multiforme

Answer

Psoriasis

Answer

Lichen planus

Answer

Lichen striatus

Question 10

Crocodile skin or sauroderma is seen in which of the following conditions?

Accepted Answer

Ichthyosis vulgaris

Answer

Toxic epidermal necrolysis

Answer

Psoriasis

Answer

Darier's disease

Basic Dermatology — MCQs

Basic Dermatology — MCQs

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